Tissue composition of major and trace elements in uremia and hypertension

Tissue composition of major and trace elements in uremia and hypertension

J Chron Dis 1974, Vol. 27, pp. 135-161. Pergamon Press. Printed in Great Britain TISSUE COMPOSITION OF MAJOR AND TRACE ELEMENTS IN UREMIA AND HYPERTE...

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J Chron Dis 1974, Vol. 27, pp. 135-161. Pergamon Press. Printed in Great Britain

TISSUE COMPOSITION OF MAJOR AND TRACE ELEMENTS IN UREMIA AND HYPERTENSION* SUCHATIINDRAPRASITt,GEORGEV. ALEXANDERIand HARVEYC. GONICK: (Received 23 July 1973)

INTRODUCTlON THERE has been growing concern with environmental health hazards, particularly in highly industrialized areas where the risk of contamination with toxic substances is great. In addition to sporadic cases of acute toxicity, there is justifiable suspicion that the pathogenesis of some diseases, especially chronic diseases of insidious onset, may be related to prolonged exposure to these substances at concentrations insufficient to produce conspicuous manifestations. A substantial proportion of the patients reaching terminal renal failure have no clearly definable etiology of their renal disease. It may be speculated that in some of these patients, who show no evidence for either an immunological or infectious basis, the nephropathy may be due to chronic exposure to as yet unidentified toxins. Various toxic chemical agents, in particular trace metals, have been shown to produce renal disease and hypertension in man and experimental animals. Huth [l], in a review article published in 1965 lists lead, cadmium, bismuth, copper, mercury, beryllium, uranium, chromium and gold. Browning [2] also includes thallium and boron amongst the potentially toxic industrial metals. Exposure is particularly high in industries concerned with mining, refining of metals, and manufacture or repair of batteries (lead, cadmium and silver), paints and pigments (lead, cadmium), electrical meters (mercury), semiconductors (lead, bismuth, copper, silver and gold), nuclear reactors (uranium, cadmium), rodenticides and pesticides (thallium, mercury, lead). glass and pottery products (lead, cadmium, bismuth, mercury and chromium). A well-documented example of chronic trace metal nephropathy is the entity known as ‘Ouch-ouch disease’. This is a Fanconi-like renal disease endemic to a rural area in Japan, discovered over 60 years ago, but recently demonstrated to be due to chronic cadmium toxicity [3]. Balkan nephropathy is another example of an endemic chronic nephropathy confined to certain areas in Rumania, Yugoslavia and Bulgaria which has been known for over 30 years. Although a toxic substance has been suspected as the etiology of this disease, none has as yet been delineated [4]. *This research was supported by Contract AT (04-l) GEN-12 from the Atomic Energy Commission and Grants-in-Aid from The Los Angeles County Heart Association, The American Heart Association, The Edna and George Castera Fund, The Louis B. Mayer Foundation for Medical Education and Research, and USPHS Grant No. 1 SOL SR-05354. tResearch Fellow in Nephrology. Present address: Faculty of Medicine, Ramathibodi Hospital, Rama VI Road, Bangkok 4, Thailand. $From the Laboratory of Nuclear Medicine and Radiation Biology and the Department of Medicine, UCLA Center for the Health Sciences, Los Angeles, California, 90024, U.S.A. Address reprint requests to Dr. Gonick. 135

136

SUCHATI INDRAPRASIT, GEORGE V. ALEXANDER and HARVEY C. GONICK

A relationship between chronic exposure to trace metals and hypertension has also been suggested. Schroeder [5] and Perry [6] have implicated cadmium as a trace metal which may have a direct bearing on essential hypertension. Hypertension is much more prevalent in highly industrialized countries such as the United States and Japan than in the underdeveloped countries of Africa. Tissue concentrations of cadmium and other trace metals are also considerably higher in the United States and Japan than in Africa [5]. The parallelism may be noteworthy. The primary purpose of the present study was to determine whether either uremia or hypertension was associated with alterations in tissue composition of trace elements. We were particularly interested in ascertaining whether there was any evidence for trace metal-induced renal disease or hypertension, but in addition, sought to determine whether potentially toxic trace elements accumulated in other organs secondary to renal failure. As a by-product of this study, we have also had the opportunity to examine alterations in the distribution of the major elements (sodium, potassium, calcium, magnesium, and phosphorous) in uremia. Review of these latter data has provided further insight into the pathophysiology of the uremic syndrome.

METHODS

AND

MATERIALS

(A) Patient pupwiatiotr Tissues for analysis were obtained from 220 random autopsies at UCLA Hospital over a I-yr period. Specimens of renal cortex were obtained from all patients and specimens of liver and spleen from the last 144 patients. The patients’ charts and autopsy protocols were reviewed and the following data were abstracted: (I) Clinical

indication

of acute or chronic

renal failure at the time of death.

(2) Entry blood pressure at the time of final admission time of the most recent prior hospital admission. (3) Serum creatinine

On the basis of these clinical groups :

(3) Chronic

findings,

serum creatinine

(2) Acute Renal

at the

at the time closest to demise,

(4) Indications from the autopsy report chronic disease of kidney, liver or spleen.

(1) Normals:

and, when available,

Failure

Renal Failure

the patient

less than

(ARF): (CRF):

of the presence population

or absence

of acute

or

was divided into three

1.5 mg ‘ii,- I16 patients.

52 patients. 52 patients.

The use of the term ‘normal’ merely refers to the observation that there was no clinical or pathological evidence of renal disease; obviously, as these patients expired following a terminal illness, they cannot be considered to be healthy normals, but do serve as controls for this study. Patients with acute renal failure were considered to be those with no pre-existent known renal disease or evidence of chronic renal disease on microscopic examination in whom azotemia occurred as a pre-terminal event secondary to acute renal injury. In most instances the clinical course clearly differentiated acute renal failure from pre-renal azotemia; evidence to support acute tubular necrosis was also obtained from the microscopic material. The mean serum creatinine in this group was 4.Ok3.6 (SD.) rng’jb with a range of 0.7-18.2 mg’$,. Patients were classified as

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

137

having chronic renal failure if there was either a clear-cut history of pre-existent renal disease or the pathological alterations in the kidney were sufFicient to warrant such a diagnosis. Diagnoses of patients falling within this group are listed in Table I. The mean serum creatinine was 4.21fi4.4 mg% with a range of 0.7-24.0 mgo,l;,. The patient population was further subdivided into normotensive (mean blood pressure less than 110 mm) and hypertensive subgroups. Furthermore, the normal and the renal failure populations were examined separately with regard to the influence of age, by dividing the patient populations into IO-yr age intervals. All statistical analyses employed the Student t-test. TABLE WITH

1.

DIAGNOSIS

CHRONIC

OF

RENAL

I 2 3 4 5 6

Nephrosclerosis Glomerulonephritis Pyelonephritis Collagen disease Diabetic nephropathy Amyloid nephropathy 7 Gouty nephropathy 8 Myeloma kidney

PATIENTS

FAILURE

26 2

II 5 5

1 I I

(B) Method of analysis To facilitate storage and handling, all tissue samples were freeze-dried. Aliquots (10 mg), approximately equivalent to 40 mg of wet tissue, were taken for analysis. In many instances replicate analyses were performed. Analyses were carried out using an emission spectrometer procedure capable of determining 25 elements frequently found in biological tissues. The sample elements were volatilized and excited in a 12 a D.C. arc. The various element signals were sorted and recorded with an ARL 1.5 m grating spectrometer. The signal data. which were automatically transferred to IBM punched cards, were processed to concentrations in ppm dry weight with an IBM 360-91 computer. The following elements were determined: sodium, potassium, calcium, phosphorus, magnesium (hereafter referred to as ‘major elements’), cadmium, zinc, copper, lead, iron, manganese, aluminium, silicon (hereafter referred to as ‘prevalent trace elements*), boron, tin, cobalt, nickel, molybdenum, titanium, chromium, strontium, barium. lithium, silver and vanadium (hereafter referred to as ‘less prevalent trace elements’). In addition, cadmium/zinc ratios were determined for each tissue because of implications by other investigators that this ratio, rather than the absolute level of cadmium, is important in determining cadmium toxicity (vide infva). The limits of detection by this method are as follows: 0.2 ppm-silver; 0.5 ppm-cadmium, copper, lead, iron, manganese, aluminium. silicon, boron, tin, cobalt, nickel, molybdenum, chromium, strontium, barium ; 1.Oppm -titanium and lithium; 2.0 ppm-calcium, magnesium and vanadium ; 3.0 ppm-zinc: 5.0 ppm-sodium; 50.0 ppm-potassium and phosphorus. The relative standard deviation for a single determination of any of these elements is 10 per cent or less.

*Elements detectable in greater than 85 per cent of tissue was detected

in only 75 per cent.

samples except Pb in kidney torte\.

which

138

SUCHATI

V.

INDRAPRASIT,GEORGE

ALEXANDER~II~

HARVEY

C.GONICK

RESULTS

(A) Normal values Table 2 contrasts the mean values for kidney, liver, and spleen in our ‘normal’ patients (age range 31-80, mean age 56) with mean values previously presented by Tipton et al. [7], accumulated from an autopsy study of 173 U.S. adults (age >20) dying an accidental death and presumably free of disease. In this table only 11 of the major and prevalent trace elements are listed (Tipton does not include data on sodium or silicon). TABLE 2. COMPARISON OF MEAN VALUES OF 'NORMAL' POPULATION OF PRESENT SERIES WITH MEANVALUESOF NORMAL’POPULATION DESCRIBED BY

TIPTONef al. [7] Kidney Element Potassium Calcium Phosphorus Magnesium Cadmium Zinc Copper Lead Iron Aluminium

Liver

T*

It

7990 461 7050 564 150.4 230 12.7 5.64 324 4.28 2.02

7230 515 7500 607 92.4 120 12.6 5.78 299 4.05 8.43

--

T*

--

7400 181 7400 481 6.66 141 25.2 5.55 555 4.81 2.41

Spleen

It

T*

It

7460 216 9400 499 14.39 159 23.7 9.81 445 9.11 12.03

11500 300 8000 500 < 2.50 70.0 4.70 < 0.5 1200 0.55 3.70

11600-250 10500 547 6.58 62.8 5.49 7.85 730 I.72 10.71

*Mean values derived from series of Tipton et al. [7] converted to ppm dry weight. tMean values from present series in ppm dry weight.

TABLE 3. NORMAL

COMPARISON OF CONCENTRATIONS OF AGE-RELATED KIDNEY CORTEX AT AGE INTERVALS WHICH SHOWED DEVIATIONS

Elements Potassium Calcium Phosphorus Cadmium Zinc

Age interval l-10 71-80 1l-20 71-80 1l-20 7 I-80 l-10 51-60 71-80 l-10 41-50 71-80

Kidney cortex concentration (ppm dry weight) 8820 6620 317 602 8750 7250 33.1 110.2 53.9 92.7 152.1 101.6

f & + -j, f i h & -+ * f +

2380’ 1910 101 164 1690 1280 26.4 69.1 28.0 39.3 68.1 34.1

+Comparison between first and second age intervals. + +Comparison between second and third age intervals. * Standard deviation.

ELEMENTS MAXIMUM

P


-t < 0.01 ++<0.01

IN

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

Ii.l-10

11-20

-[-7--.. 21-30

r-II.

31-40

Age

41-50

51-60

139

.~ 61-70

71-60

~80

Interval

FIG. 1. Relationship of kidney cortex content of cadmium to age. Plotted are means + S.E. Similar age relationships were noted for kidney cortex content of zinc, copper, lead and aluminium.

(B) Effect oj’ age The normal group was divided into 10 yr age intervals and mean values of each age interval were plotted against age for the 13 elements in the major and prevalent trace elements groups. Of the three organs that were analyzed, age relationships were most apparent in kidney cortex. In several instances (cadmium, zinc, copper, lead and aluminium) the elemental content reached a peak at an intermediate age group (40-60) and then subsequently decreased to a level approximately equal to that seen in the 10-20 yr age group (Fig. 1). In other instances, there was a gradual decrease with age (potassium and phosphorus) (Fig. 2) or increase with age (calcium) (Fig. 3). No

6,OOOj

Y

4,000-J

,--<,

lTml-10

11-20

T ~---l-in 21-30 31-40

Age

FIG.2.

Relationship

41-50

51-60

61-70

71-80

>80

Interval

of kidney cortex content of phosphorus

and potassium to age.

140

SUCHATI

INDRAPRASIT,GEORGB

V. ALEXANDER~~~

HARVEY C. GONICK

age-dependent relationships were noted for sodium, magnesium, silicon, iron and manganese. Table 3 presents a statistical comparison of concentrations of age-related elements in kidney cortex at the age intervals at which maximum deviations were seen.

E 700-

)

B

500E .? U s 400? .z 300-

BO Age

FIG. 3.

(C) Abnormalities

Relationship

ofmajor

of kidney

Interval

cortex

content

of calcium

to age.

elements in uremia

(1) Comparison of mean values in total group, age 31-80. Table 4 presents the mean vahres, standard deviations and t-test comparisons for the major elements in normals, patients with ARF, and patients with CRF. This table includes only individuals age 31-80, as very few patients under the age of 30 or over the age of 80 fell into the ARF and CRF groups, whereas a substantial proportion of the normals were under age 30 (Fig. 4). The adjusted mean ages for normal, ARF, and CRF groups were 56. 53 and 59, respectively. 25-

I Normals

20-

G 155 s E IO-

5-

nO-I

FIG. 4.

Distribution

l-10

of normals

11-20 21-30 31-40 4l-50 51-60 61-70 71-60 >80 Age Interval

and patients

with acute renal failure interval.

and chronic

renal failure

by age

Sodium content of kidney cortex was significantly increased in both the ARF and CRF groups. There was no difference between these two subgroups of the renal failure population. Sodium content of liver and spleen was increased in CRF but not in ARF.

2560 3110 2990

2100 2160 2500

198 260 335

1570 1880 1340

241 214 173

7230 7120 6750

515 625 653

7500 7520 7580

607 597 559

S.D.

10,000 12,100 11,500

Mean *

or CRF.

134 74 86

132 73 87

134 73 86

137 74 90

135 74 87

Kidney n

N.S.

N.S.

N.S. N.S.

< 0.01

< 0.01

N.S. N.S.

i 0.01

< 0.01

P’

N.S.

N.S.

N.S.

N.S.

N.S.

P"

499 561 559

9400 10,800 9980

216 232 277

7460 7840 7350

5880 6440 7030

Mean *

208 194 204

3290 4190 1900

116 131 130

2250 2050 2520

2080 2410 2600

S.D.

91 42 76

91 44 76

91 44 72

92 44 74

92 44 76

Liver n

N.S. N.S.

N.S. N.S.

N.S. i 0.01

N.S. N.S.

N.S. < 0.01

P’ _~

COMPARISONOFTISSUECOMPOS~PIONOFMAJOR ELEMENTSIN NORMALS,PATIENTSWII-HACUTERENAL

P’ ==Comparison of normals with ARF P”--Comparison of ARF with CRF. * ---ppm dry weight.

Sodium Normals ARF CRF Potassium Normals ARF CRF Calcium Normals ARF CRF Phosphorus Normals ARF CRF Magnesium Normals ARF CRF

Element

TABLE 4.

N.S.

N.S.

N.S.

N.S.

< 0.001

P”

547 515 521

10,500 12,700 11,300

250 320 289

11,600 10,000 10.000

6350 6250 7040

Mean *

143 184 202

7090 5550 3900

126 203 170

3410 2310 2890

1960 1560 2460

S.D.

90 38 76

91 40 76

91 40 78

92 40 76

92 40 76

Spleen n

FAII.UREANDPATIENJSWW~THCHRONIC

N.S.

N.S.

N.S.

N.S.

< 0.05 N.S.

i 0.01

< 0.01

< 0.05

N.S.

P’

N.S.

N.S

N.S.

N.S.

< 0.005

P”

RENALFAILURL

0.77 0.77 0.67

12.6 9.23 11.4

5.78 4.02 5.07

Copper Normals ARF CRF

Lead Normals ARF CRF

120 103 113

92.4 79.1 75.2

Mean*

Cadmium/Zinc Normals ARF CRF

Normals ARF CRF

ZiilC

Cadmium Normals ARF CRF

Element

6.78 2.07 3.49

6.35 4.47 5.54

0.45 0.46 0.41

49.4 42.1 58.5

59.8 54.1 47.8

SD.

119 52 66

135 73 88

79 41 46

133 74 88

134 73 88

Kidney n

< 0.02 N.S.

N.S.

< 0.01

N.S. N.S.

N.S.

< 0.01

N.S. < 0.02

P

i 0.05

< 0.01

N.S.

N.S.

N.S.

P”

9.81 13.7 11.3

23.7 22.4 22.8

0.07 0.05 0.05

1.59 202 201

14.4 20.0 14.8

Mean*

RENAL

6.78 10.3 7.79

13.1 9.85 11.6

0.12 0.04 0.03

10.2 92.8 95.0

7.99 14.0 8.47

S.D.

FAILURE

87 43 75

92 44 76

52 22 39

91 44 75

91 43 75

Liver n

< 0.05 N.S.

N.S. N.S.

N.S. N.S.

< 0.01

< 0.01

< 0.02 N.S.

P’

N.S.

N.S.

N.S.

N.S.

i 0.05

P”

7.85 12.6 8.81

5.49 6.02 5.51

0.06 0.09 0.06

62.8 75.8 72.3

6.58 12.0 8.38

Mean*

8.79 9.63 7.84

1.58 2.22 1.88

0.03 0.06 0.05

21.8 29.3 30.4

4.11 11.4 11.4

S.D.

83 36 68

92 40 76

50 20 38

92 40 76

89 36 73

Spleen n

TABLE 5. COMPAREONOFTISSUECOMPOSI~ONOF‘PREVALENT'TRACEELEMEN~SINNORMALS,PA~ENTSWITHAC~RENALFA~LUREANDPAT~ENTS\KITHCHRON~C

< 0.02 N.S.

N.S. N.S.

< 0.05 N.S.

< 0.01
N.S.

< 0.01

P’

4 0.05

N.S.

< 0.01

N.S.

N.S.

P”

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

143

144

SIJCHATI INDRAPRASIT, GEORGEV.

ALEXANDER

and

HARVEY C. GONICK

There were no significant differences in potassium content of kidney cortex or liver; however, potassium content of spleen was significantly reduced in both ARF and CRF, with no differences between these two subgroups. Calcium content of kidney cortex was significantly increased in both ARF and CRF, and there were no differences between these two subgroups. Calcium content of liver was increased in CRF but not in ARF, whereas calcium content of spleen was increased in ARF but not in CRF. Phosphorus and magnesium content of all three organs remained normal in ARF and CRF. When the normal values presented by Tipton et al. [7] rather than the ‘normal’ values of the present series are used for comparison with the renal failure subgroups, deviations from normal follow the same trend, but in some instances are more striking. In particular, a decrease in potassium content of kidney cortex and increases in calcium and phosphorus content of kidney cortex and liver in the presence of renal failure are noteworthy. (2) Comparison of kidney cortex content of major elements at specific age intervals. A relationship to age had previously been noted within the normal group in kidney cortex content of potassium, calcium, and phosphorus. Calcium content of kidney cortex increases with age in ARF and CRF in the same manner as it does in the normal group. In contrast, there is less tendency toward an age relationship in potassium and phosphorus content of kidney cortex in both the ARF and CRF groups.

13,000f d ?i 6 12.000E g z 2 g I1 ,ooo” E z! z m $7 10,000.g I I I 0.4-0.6 0.7-0.60.9-1.1

I 121.9

I 2.1-2.8

/ I --1-1 3.0-4.8 5.0-7.8 8.1-10.512.0-24.0

Serum Creotinine

Fco. 5.

Relationship of kidney cortex content of sodium and calcium to degree of azotemia.

(3) Correlation of kidney cortex content of major elements with degree of azotemia. Patients from all three populations (normal, ARF and CRF) were grouped according to serum creatinine values, in intervals designed to maintain a reasonably uniform distribution of sample size. There was no apparent correlation of kidney content of phosphorus, potassium or magnesium with serum creatinine. Kidney content of

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

145

sodium and calcium, on the other hand, showed a tendency to increase with increasing degrees of azotemia (Fig. 5). In addition, it was noted that kidney content of calcium, in particular, increased early in the course of renal failure. Kidney content of calcium in patients with serum creatinine ranging from 2.1 to 2.8 mg% was 601+230 (S.D.) ppm dry weight compared to kidney content of calcium in patients of same age range with serum creatinine from 0.9 to 1.1 rng% of 494& 186 ppm dry weight (significant difference at p < 0.05). The calcium content of liver and spleen also tended to increase early in the course of renal failure, although the levels did not reach statistical significance (liver: mild azotemia 282 + 152, normal 213 f 178, p < 0.10; spleen : mild azotemia 3 17 + 161, normal 253 _+127, p < 0.20). (D) Abnormalities of trace elements in uremia (1) Comparison with normals, age 31-80. Table 5 presents the mean values, standard deviations and t-tests of the prevalent trace elements in normals, ARF and CRF. Cadmium content of kidney cortex is decreased in CRF and normal in ARF. Cadmium content of liver and spleen is increased in ARF and normal in CRF. Zinc content of kidney cortex is decreased in ARF and normal in CRF. Zinc content of liver and spleen is increased in both ARF and CRF. The cadmium/zinc ratio is normal in all groups with the exception of an increase in the spleen in ARF. Copper content is decreased in kidney cortex of ARF and normal in all other groups. Lead content of kidney cortex is decreased in ARF and normal in CRF. Lead content of liver and spleen is increased in ARF and normal in CRF. Iron content of kidney cortex is normal in both ARF and CRF while the iron content of both liver and spleen is increased in ARF and increased in liver in CRF. Manganese content of kidney cortex is decreased in CRF and normal in ARF. Manganese content of liver is normal in both ARF and CRF but increased in the spleen in ARF. Aluminium content is normal in all groups. Silicon content is increased in all groups with the exception of spleen in ARF. Table 6 presents the percentage detectability and mean values for the less prevalent trace elements. In this table we record all samples analyzed (including replicates and including all age groups). Although the number of samples in which detectable values were found is too small for valid statistical comparisons, we should like to make some general comments concerning deviations from normal based on both per cent detectability and mean values in the patient subgroups. Nickel content of spleen appears to be increased in both ARF and CRF. Molybdenum content of spleen may be increased in ARF. Tin content of kidney cortex and liver and chromium content of kidney cortex may be increased in CRF. None of the other elements (Co, Sr, Ba, Li, Ag, Va and Bo) showed consistent directional changes in per cent detectability and mean values. An attempt was made to ascertain whether any of the patients with ARF or CRF might have had renal disease induced by accumulation of trace elements. In order to explore this possibility we carefully reviewed each case in which the trace element content of kidney cortex was greater than three times the standard deviation from the mean. In the case of the less prevalent elements, a scattergram of the results was visually examined and those cases at the extreme higher end of the distribution were selected for review.

SUCXATIINDRAPIXASIT, GEORGEV. ALEXANDERand HARVEY C. GONICK

146 TABLE 6.

COMPARISON

PATIENTS

WITH

OF TISSUE ACUTE

Elements

COMPOSITION

RENAL

FAILURE

Kidney % Detectability

Mean*

OF AND

‘LESS

PREVALENT’

PATIENTS

Liver % Detectability

WITH

TRACE CHRONIC

ELEMENTS RENAL

IN

NORMALS,

FAILURE

Spleen % Detectability Mean*

Mean*

Titanium Normals ARE CRF

10 10

1.44 1.52 1.31

4 2 6

3.09 1.24 1.95

11 9 9

1.84 2.94 1.90

Cobalt Normals ARF CRF

11 13 15

1.12 1.03 1.55

11 14 19

1.06 1.17 0.97

10 9 9

1.08 0.97 1.02

Nickel Normals ARF CRF

1.82 1.86 1.82

16

:; 34

:z

1.85 2.14 1.95

16 38 40

1.72 2.11 1.97

Molybdenum Normals ARF CRF

13 23 25

1.91 1.92 2.11

12 86 84

3.42 4.99 5.01

28 52 41

3.47 4.80 3.21

Tin Normals ARF CRF

31 44 55

1.03 1.03 1.44

66 70 86

1.83 1.69 2.53

45 61 70

1.19

Chromium Normals ARF CRF

:; 58

4.61 3.21 6.56

45 41 29

2.17 3.86 3.82

40 42 34

6.72 2.11 5.37

Strontium Normals ARF CRF

106 30

1.51 0.35 0.44

2 3 1

0.18 0.31 0.50

6 5 6

0.44 0.39 0.59

Barium Normals ARF CRF

13 15 I

0.96 1.21 10.8

9 6 11

1.17 0.28 10.8

13 13 16

2.38 0.77 1.52

Lithium Normals ARF CRF

43 32 16

76.0 83.0 89.8

42 27 16

19.2 81.6 57.5

43 21 14

Silver Normals ARF CRF

11 6 5

0.36 0.81 0.18

13 6 7

0.70 4.66 7.61

9 3 7

2.68 1.02 3.78

Vanadium Normals ARF CRF

2 3 3

2.87 2.45 1.96

1 2 2

2.20 1.71 1.63

1 0 0

1.69 -

Boron Normals ARF CRF

13 34 33

0.94 1.15 1.45

33 55 59

2.31 3.03 1.83

*ppm dry weight.

8



52 17 83

::z

75.6 85.9 70.8

2.51 5.01 2.79

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

147

No instances of unusual accumulation of cadmium, zinc, copper, lead, aluminium, titanium, nickel, molybdenum, strontium, lithium, silver, vanadium or boron were noted. Very high iron levels were seen in two patients from the normal group, two patients with ARF and one patient with CRF. Manganese concentration was unusually elevated in one patient with ARF. Abnormally elevated silicon content was found in two patients with ARF. Cobalt was found to be disproportionately increased in the kidney (but not liver or spleen) in one patient with CRF. This patient was a 35-yr-old female with juvenile diabetes in her 28th week of pregnancy, who died of a viral pneumonia. On pathologic examination, the kidney showed mild diabetic nephropathy. Exceptionally high levels of tin were also found in this patient’s kidney and spleen. Three additional CRF patients demonstrated very high tin levels in the kidney. Chromium concentration was markedly increased in two patients with CRF. Barium content of kidney was very high in one patient with ARF and one patient with CRF. In none of these cases was it possible to attribute the kidney disease to trace element accumulation. (2) Examination of trace element alterations in kidney cortex in uremia at speciJc age intervals. As cadmium and zinc both show a curvilinear relationship with age in normals (particularly in kidney cortex), it was decided to compare the normal and pathological groups at both peak and low values. The statistical comparisons are presented in Table 7. At ages 3 l-60 (peak values) kidney cortex content of cadmium is decreased in both ARF and CRF, while at ages 61-80 (low values) there is no difference between the patient subgroups and the normal population. TABLE 7.

Elements

CONCENTRATIONSOFCADMKJMANDZINCIN

Age intervals

Cadmium

31-60

61-80

Zinc

31-50

51-80

KIDNEY CORTEXATSPECIFIC AGEINTERVALS

Group Mean*

SD.

Kidney n

P’

P”

Normal ARF CRF

106.7 73.5 75.9

65.5 52.7 49.4

80 53 50

< 0.01 < 0.01

N.S.

Normal ARF CRF

71.2 93.9 74.2

41.8 56.3 44.7

54 20 38

N.S. N.S.

N.S.

Normal ARF CRF

149.7 98.3 92.0

63.2 43.8 42.0

37 34 22

< 0.01
N.S.

Normal ARF CRF

108 107 120

37.4 40.8 61.8

96 40 66

N.S. N.S.

N.S.

*ppm dry weight.

(3) Correlation of kidney cortex content of trace elements with degree of azotemia. Two elements showed a tendency to increase with advancing azotemia (aluminium and silicon, Fig. 6) within an intermediate range of serum creatinine, but aluminium levels decreased again at serum creatinine levels above 10 mg% while silicon continued to increase. Three elements showed a tendency to decrease with advancing azotemia (copper, cadmium, and lead, Fig. 7).

148

SUCHATIINDRAPRASIT, GEORGEV. ALEXANDER and HARVEYC. GONICK

0.4-0.6

0.7-0.6

M-l.,

/ , , , j,, 1.2-1.9

2.1-28

3.0-4.6

5.0-7.3

8.1-10.5

12.0-24.0

Serum Creatinine

Fw. 6.

Relationship

(E) Abnormalities

of kidney cortex content of silicon and aluminium to degree of azotemia.

of major and trace elements in hypertension

Only measurements in the age group from 31-80 are included. Both the normal group and uremic (CRF only) group were divided into hypertensive and normotensive sub-populations, defining hypertension as a mean blood pressure of r: 110 mm Hg. The composition of each subgroup is as follows: (1) Normal group-Normotensive: 71 patients, age range 34-80 and mean age 55. -Hypertensive: 10 patients, age range 42-80 and mean age 62. (2) Uremic group-Normotensive: -Hypertensive:

31 patients, age range 33-79 and mean age 59. 14 patients, age range 41-79 and mean age 60.

Values are presented in Tables 8-l 1.

t-2

0

j

, 0.4-0.6

I 0.7-0.6

Lwd I 0.9-1.1

I 1.2-1.9

I 2.1-2.6

I 3.0-4.6

I 5.0-7.6

I 6.1-10.5

1 12.0-24.0

Serum Creatinine

FIG. 7.

Relationship

of kidney cortex content of copper, cadmium and lead to degree of azotemia.

533 415

7490 7510

613 545

Calcium Normotensive Hypertensive

Phosphorus Normotensive Hypertensive

Normotensive Hypertensive

dry weight.

1200 7350

Potassium Normotensive Hypertensive

lppm

10,100 9430

Mean*

Normotensive Hypertensive

sodium

Element

TABLE 8. COMPAIUWN

Kidney

245 208

1620 1070

201 117

2860 2699

2650 2060

S.D.

118 18

116 18

118 18

121 18

119 18

n

N.S.

N.S.

< 0.01

N.S.

N.S.

P

505 465

9470 8990

225 162

7460 7410

6030 5030

Mean*

OFTISSUECOMPOSITION OFMAJORELEMENWIN

211 182

3190 3660

117 89

2260 2120

2110 1520

S.D.

Liver

NORMOTENSWE

78 15

18 15

78 15

79 15

79 I5

n

N.S.

N.S.

-=z0.05

N.S.

< 0.05

P

517 417

10,100 13,200

261 201

11,400 11,300

6550 5560

Mean*

128 155

6970 6960

126 113

5250 2390

2010 1430

S.D.

76 16

78 15

71 16

18 16

78 16

n

NORMALGROUP

Spleen

AND HYPERTENSIVE SUB-POPULATIONSOFTHE

< 0.01

N.S.

N.S.

N.S.

< 0.05

P

5.71 5.65

Lead Normotensive Hypertensive

14.1 14.2

Silicon Normotensive Hypertensive

dry weight.

7.48 14.5

Aluminium Normotensive Hypertensive

lppm

4.27 3.05

Manganese Normotensive Hypertensive

298 293

12.8 11.2

Copper Normotensive Hypertensive

Iron Normotensive Hypertensive

0.72 0.78

Normotensive Hypertensive

CadmiUlll/ZiflC

121 140

Zinc Normotensive Hypertensive

Mean*

OF TJSSUE

92.3 90.3

COMPARlSON

Cadmium Normotensive Hypertensive

Element

TABLE 9.

Kidney

12.2 18.8

16.4 27.4

3.35 1.52

91.7 96.3

7.05 4.39

6.63 3.51

0.28 0.47

44.5 46.8

61.8 41.5

S.D.

COMPOS~ON

114 18

117 17

117 18

121 16

105 16

119 18

69 10

113 18

118 18

n

N.S.

N.S.

< 0.02

N.S.

N.S.

N.S.

N.S.

N.S.

N.S.

P

OF ‘PREVALENT

ELEMENTS

13.9 10.2

12.8 8.65

9.46 8.85

440 476

9.73 9.77

24.6 18.0

0.08 0.05

154.3 185.2

15.1 16.2

Mean*

TRACE

14.9 8.0

21.3 5.39

3.65 4.53

414 148

6.63 7.42

13.6 6.88

0.13 0.05

70.7 59.3

8.28 16.6

S.D.

Liver

78 15

65 15

68 15

78 15

74 15

79 15

44 8

78 15

77 16

II

IN NORMOTENSIVE

AND

N.S.

N.S.

N.S.

N.S.

N.S.

< 0.01

N.S.

N.S.

N.S.

P

9.46 12.0

5.52 5.42

0.05 0.08

60.4 73.9

6.06 9.24

26.6 33.7

10.0 7.70

1.42 1.88

29.5 36.1

19.3 7.09

1.90 1.55

261 301

8.73 13.0

1.59 1.53

0.02 0.03

21.0 21.9

3.84 4.30

S.D.

SUB-POPULATIONS

Mean*

705 846

HYPERTENSIVE

Spleen

78 16

78 16

69 14

76 16

70 15

78 16

42 8

78 16

75 16

n

OF THB

NORMAL

N.S.

N.S.

N.S.

N.S.

N.S.

N.S.

< 0.05

-=z 0.05

< 0.01

P

GROUP

6650 6990

573 843

7530 7790

567 530

Potassium Normotensive Hypertensive

Calcium Norrnotensive Hypertensive

Phosphorus Normotensive Hypertensive

Magnesium Normotensive Hypertensive

*ppm dry weight.

11,600 11,400

Kidney

181 157

1040 2130

215 456

2550 2030

2930 3110

SD.

59 30

60 30

59 30

63 30

60 30

n

N.S.

N.S.

< 0.01

N.S.

N.S.

P

551 573

9820 10,300

284 264

7060 7940

1220 6660

Mean*

197 220

1460 2560

108 122

2430 2650

2960 1710

S.D.

OF-I-ISSUECOMPOSITION OF MAJOR ELEMENTS IN NORMOTENSWE

Sodium Normotensive Hypertensive

COMPARISON

Mean*

10.

Element

TABLE

Liver

50 26

50 26

46 26

49 2.5

50 26

n

N.S.

N.S.

N.S.

N.S.

N.S.

P

511 539

10,800 12,200

255 361

10,200 9740

6960 7190

Mean*

AND HYPERTENSIVE SUB-POPULATIONS

204 201

3490 4510

(CRF)

50 26

50 26

53 25

50 26

50 26

n

UREMIC

Spleen

41.9 161

2800 3130

2470 2500

SD.

OFTHE

N.S.

N.S.

< 0.01

N.S.

N.S.

P

GROUP

11.

4.95 4.83

Lead Normotensive Hypertensive

13.1 15.6

22.7 25.6

Aluminium Normotensive Hypertensive

Silicon Normotensive Hypertensive

*ppm dry weight

3.38 2.53

Manganese Normotensive Hypertensive

285 270

12.0 9.55

Copper Normotensive Hypertensive

Iron Normotensive Hypertensive

0.71 0.58

136 105

79.6 62.5

Cadmium/Zinc Normotensive Hypertensive

zinc Normotensive Hypertensive

OF TISSUE

Mean*

COMFARJ,KIN

Cadmium Normotensive Hypertensive

Element

TABLE

20.6 31.7

20.5 27.0

2.11 1.41

80.2 153.9

3.72 3.06

6.33 3.01

0.39 0.24

31.9 58.8

-

Kidney

47.6 47.2

S.D.

COMPOSITION

59 30

61 28

61 26

60 30

47 22

61 30

32 14

51 30

61 30

n

N.S.

N.S.

< 0.05

N.S.

N.S.

< 0.02

N.S.

< 0.01

N.S.

P

OF ‘PREVALENT

19.6 27.7

13.4 12.1

8.84 10.7

495 567

10.5 12.9

20.3 27.6

0.05 0.04

178 246

13.9 16.5

25.5 31.5

15.1 10.8

3.95 5.59

176 183

8.13 6.98

10.6 12.0

0.04 0.01

72.0 115.7

7.26 10.3

Liver

50 26

50 25

50 26

50 26

49 26

50 26

26 13

49 26

49 26

n

IN NORMOTENSIVE

S.D.

GROUP

ELEMENTS

Mean*

TRACE

AND

N.S.

N.S.

N.S.

N.S.

N.S.

< 0.01

N.S.

< 0.01

N.S.

P

37.9 44.3

17.5 13.3

1.31 3.57

752 897

7.25 11.5

5.16 6.19

0.06 0.07

65.2 85.3

6.64 11.5

33.2 35.0

21.2 17.4

0.80 5.03

241 325

4.28 11.3

1.65 2.13

0.03 0.07

17.7 37.9

4.01 18.1

S.D.

50 26

50 26

42 21

50 26

43 25

50 26

25 13

49 27

47 26

n

OF THE

Spleen

SUB-POPULATIONS

Mean *

HYPERTENSIVE

N.S.

P

(CRF)

N.S.

N.S.

< 0.05

< 0.05

N.S.

< 0.05

N.S.

< 0.02

UREMIC

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

153

(1) Normal group (hypertensives vs. normotensives). (a) Major elements (Table 8). Sodium content of liver and spleen is decreased in the hypertensive population; sodium content in kidney, however, is within the normal range. Potassium levels are normal in all three organs. Calcium is decreased in kidney and liver, but normal in spleen. Phosphorus is normal in all three organs. Magnesium is decreased in spleen but normal in kidney and liver. (b) Trace elements (Table 9). Cadmium is increased in the spleen, but normal in kidney and liver. Zinc is increased in spleen, but normal in kidney and liver. The cadmium/zinc ratio is also increased in spleen but normal in kidney and liver. Copper is decreased in liver but normal in kidney and spleen. Lead is normal in all three organs. Iron is normal in all three organs. Manganese is decreased in kidney but normal in liver and spleen. Aluminium is normal in all three organs. Silicon is normal in all three organs. (2) Uremic group (hypertensives vs. normotensives). (a) Major elements (Table 10). Sodium, potassium, phosphorus and magnesium concentrations show no significant difference between hypertensive and normotensive subpopulations in any of the three organs. In kidney and spleen calcium concentration is increased in the hypertensive subgroup while in liver the calcium concentration is approximately the same in each group. (b) Trace elements (Table 11). Cadmium concentration is roughly equal in hypertensive and normotensive sub-populations in all three organs. In the hypertensive sub-population, zinc is decreased in kidney, increased in liver and spleen. The cadmium/zinc ratio is equal in the two population subgroups in kidney, liver and spleen. Copper concentration is decreased in kidney but increased in liver and spleen in the hypertensive subgroup. Lead concentration is equal in both subgroups in all three organs. Iron concentration is increased in spleen in the hypertensive subgroup but equal to the normotensive subgroup in kidney and liver. Manganese concentration is increased in spleen in the hypertensive subgroup but equal to the normotensive subgroup in liver and decreased in kidney. Aluminium and silicon concentrations are equal in the subgroups in all three organs. DISCUSSION

{A) Norma/ values Many of our ‘normal’ values fall within 10 per cent of the values determined by Tipton et al. [7]. Exceptions were phosphorus, cadmium, lead, manganese and aluminium, which were higher in liver and spleen in the present series, and iron, which was lower in liver and spleen. In the kidney, cadmium and zinc were lower in the present series, whereas aluminium was higher. A possible explanation for the discrepancy in kidney cadmium and zinc is that the Tipton series may have been weighted toward the 40-60 yr age range, when these elements reach maximal levels (vide infra). No comment can be made concerning the discrepancies in liver and spleen values as the present series included several patients with disease of one or both of these organs. (B) E@ct qf age Kidney content of cadmium, zinc, copper, lead and aluminium increased with age, reaching peak values at ages 4&60, whereas kidney content of calcium increased and kidney content of potassium and phosphorus decreased throughout the life span.

154

SUCHATIINDRAPRASIT, GEORGEV. ALEXANDER and HARVEYC. GONICK

Age-dependent relationships have been reported by others. Allen et al. [8] measured total body potassium by counting the y-rays emitted from the natural isotope K,, in a large liquid scintillation counter. These authors found an abrupt increase in total body potassium from 0 to 10 yr, and then a gradual decrease from 10 to 80 yr of age in both males and females. Tipton et al. [9] have also examined the effect of aging on elemental composition in several organs from individuals dying from accidental deaths. These authors reported a gradual increase in the calcium content of kidney and a decrease in copper and manganese content of liver with age. Schroeder et al. [lo] demonstrated earlier that cadmium and zinc content of kidney peak at the age interval of 40-50 and fall off thereafter to age 80. Griffith, Butt and Walker [I l] found that copper reaches a peak in both kidney and spleen at age 40-50, whereas a more uniform age distribution was seen in liver. Iron content of spleen was found to peak at age 61-70 but no age relationship was seen in liver and kidney. Maximum lead content was found in the 40-50 age group in kidney, the 50-60 age group in liver, and the 60-70 age group in spleen. No definite age relationship was seen in these three tissues for manganese or zinc. The decreasing levels of phosphorus and potassium in our series suggest diminution of intracellular mass with aging. Increasing levels of calcium with age is an interesting phenomenon, which may represent a non-specific reaction to injury seen with degeneration or may represent calcium deposition in blood vessels as part of the atherosclerotic process. The five trace elements which show a peak level at age 40-60 and fall-off thereafter could conceivably represent environmental exposure to these elements with gradual deposition in vital organs. The fall in trace element content after age 60 may indicate that longevity depends in part on a lesser exposure to these potentially toxic elements. (C) Abnormalities of major elements in uremia

The major element abnormalities in uremia may be summarized as follows: (1) Both ARF and CRF are associated with increased sodium content of kidney cortex, decreased potassium content of kidney cortex and spleen, increased calcium content of kidney cortex and liver and increased phosphorus content of all three organs; magnesium content is unchanged. These conclusions are based on comparisons of the uremic population with our ‘normal’ group (who died of diseases not including the kidney) and with Tipton’s more accurately defined normal group, who died of accidental causes. (2) The primary difference between ARF and CRF is an increased sodium content in liver and spleen in the latter group but not the former group. The majority of previous studies of distribution of major elements in uremia have been confined to red blood cells and muscle. Most investigations have indicated an increased content of sodium [ 121, although one recent study [13] has contradicted these findings. The potassium content of red blood cells in chronic uremia has been stated to be low [ 14,151 or normal [ 161.The phosphorus [ 171and magnesium [ 18-201 content of red blood cells are increased in uremia, while calcium content is decreased [20]. Bergstrom and Bittar [21] have demonstrated increased sodium and normal potassium and phosphorus content in muscle from patients with acute renal failure but normal sodium and increased potassium and phosphorus content in muscle from patients with chronic renal failure. Magnesium content was also found to be increased. On the other hand, Lim et al. [22] demonstrated decreased muscle magnesium in chronic renal

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

155

In experimental acute renal failure in rats both sodium and potassium content of brain were found to be increased ; sodium content was also increased in muscle and liver [23]. High calcium and low sodium were described in brain tissue of dogs with acute renal failure [24]. Post-mortem examination of skin, muscle, liver, spleen, lung and heart has shown increased calcium and magnesium content in these organs in chronic renal failure [25, 261. Skin biopsies from patients with chronic renal failure have also demonstrated increased calcium content [27]. Total body potassium content measured by whole-body monitoring has been found to be normal in uremia [28] whereas exchangeable potassium tends to be low [29]. The changes in tissue sodium and potassium are compatible with the hypothesis previously advanced by Welt [12] that uremia is associated with a defect in active transport through a primary inhibition of the transport enzyme, Na-K-ATPase, resulting in an increase in intracellular sodium and a decrease in intracellular potassium. In addition, Bourgoignie, Klahr and Bricker [30] have demonstrated the presence of an inhibitor of active transport in uremic serum by measurement of changes in short circuit current across an anuran membrane and by changes in p-aminohippurate uptake by rabbit kidney cortex slices. This inhibitor was equated with Third Factor (natriuretic hormone), the humoral substance previously shown to be increased following extracellular volume expansion [31-361. Preliminary experiments from our laboratory have also suggested that Third Factor may be an inhibitor of Na-K-ATPase [37]. * Soft tissue calcification is a frequent finding in the secondary hyperparathyroidism of uremia, involving skin, vessels and periarticular tissue [27]. The factors involved in the dystrophic calcification are not entirely clear, although the elevated calcium-phosphate product in the extra-cellular fluid and increased circulating parathormone per se are probably important contributors [38]. It was of interest to note in the present series that calcium content of kidney cortex was elevated early in renal failure, before any change in the calcium-phosphate product would be anticipated. On the other hand, it is now well recognized that elevation in serum parathormone activity is found even with mild azotemia [39]. Parathyroidectomy prevents calcium deposition in the renal allograft of hypercalcemic post-transplant patients and in the kidney of experimental renal failure rats [40, 411. Reversal of soft tissue calcification has been noted after subtotal parathyroidectomy and to a limited degree after adequate hemodialysis [27]. The elevation in serum phosphate (and increased soft tissue deposition of phosphorus) in uremia may be a result not only of decreased phosphate clearance, but also a manifestation of secondary hyperparathyroidism. Serum phosphate levels tend to fall after subtotal parathyroidectomy in such patients [27]. failure.

(D) Abnormalities of trace elements in uremia In general, chronic renal failure was associated with a decrease in kidney cortex content of cadmium and manganese; in addition, there was a decrease in kidney cortex content of zinc when comparison was restricted to the age interval 31-50. Other *An alternative explanation is that resulting from a decreased filtered levels of Third Factor represents discriminate between intracellular these alternatives.

retention of sodium in the extracellular space is the primary event, load of sodium in renal failure, and that the increase in circulating a response to extracellular volume expansion. As our data do not sodium and extracellular sodium, we cannot distinguish between

156

SUCHATI INDRAPRASIT, GEORGEV. ALEXANDERand HARVEY C. GONICK

elements in the kidney were normal, with the exception of silicon, tin and chromium, which were found to be increased. Acute renal failure was associated with a decrease in kidney cortex content of zinc and copper and an increase in kidney content of silicon. Renal failure led to an increase in several elements in liver and spleen, including cadmium, zinc, iron, lead, manganese and silicon. Although differences in aluminium content did not reach levels of significance, values tended to be higher in kidney and spleen in renal failure and there appeared to be a correlation between serum creatinine levels and kidney cortex content of aluminium. When Tipton’s normal values are used, the discrepancies between our renal failure patients and normals are exaggerated (with the exception of iron in,liver and spleen, which normalizes). No evidence for trace metal-induced renal disease was found in the present series. There has been little previous documentation of changes in trace element composition in uremia. Schroeder [5] has previously found a decrease in kidney cortex content of cadmium in patients dying with renal failure of varying etiologies. Parsons et al. [42] have described an increased aluminium content of bone in patients dying of uremia, apparently unrelated to prior ingestion of aluminium-containing compounds. Berlyne et al. [43] and Thurston et al. [44] have emphasized the increased aluminium retention which occurs in experimentally uremic animals exposed to modest doses of aluminium salt. Although little is known of aluminium toxicity, these findings may have relevance to the common clinical practice of treating the phosphate retention of uremic patients with aluminium-containing antacids. A study of an endemic nephropathy in Japan, called ‘Ouch-ouch disease’, revealed osteomalacia with glycosuria, aminoaciduria and proteinuria. Cadmium was suspected to be the etiologic factor due to the finding of high cadmium in rice and soybeans grown in the endemic area. A mining plant for cadmium, lead and zinc was found to be situated upstream from the endemic area. In addition, the patients with the disease had greater concentration of cadmium in the urine than did people from non-endemic areas or control areas, whereas urine concentrations of other metals such as lead and zinc were normal. Blood and tissue cadmium levels were also found to be increased [3, 45471. In another instance of endemic nephropathy which affects certain areas of Bulgaria, Yugoslavia and Romania (‘Balkan nephropathy’), trace elements have been suspected as etiological agents. At autopsy, Makarov, Topakbashyan and Dinev [48] found abnormally high mean concentrations in the kidney of aluminium, tin, nickel and chromium, and single instances of increased levels of lead, cadmium, manganese, titanium, barium and bismuth. In most cases, cadmium content of kidney was reduced. These findings in general agree with those of the present study and do not point to significant differences in trace metal content of kidneys from patients with Balkan nephropathy when contrasted to patients with classical kidney disease. Circumstantial evidence had earlier suggested a role for cadmium in Balkan nephropathy. This evidence included a markedly increased content of cadmium in fertilizer used in the endemic areas of Yugoslavia and a moderately increased cadmium content of plants grown with the fertilizer. In addition, tubular abnormalities including tubular proteinuria, aminoaciduria, and glycosuria, similar to those previously noted in alkaline battery workers with cadmium-induced nephrotoxicity [49] were found in some patients with Balkan nephropathy [50]. The kidney pathology is also predominantly tubulointerstitial [50]. Thus, although cadmium cannot be etiologically incriminated,

Tissue Composition

of Major and Trace Elements in Uremia and Hypertension

157

it would appear likely that Balkan nephropathy is related to exposure to some other toxin which affects the proximal tubule predominantly, perhaps a heavy metal not included in the analysis. Accumulation of certain trace elements may be anticipated in renal failure as a result of decreased renal excretion. Schroeder [51] lists the following trace elements which are normally excreted principally by the kidney: germanium, rubidium, strontium, molybdenum, cadmium, cesium, boron, silicon, arsenic and selenium. Bruine et al. [52] compared the levels of certain trace metals in the blood of normal and uremic humans by means of neutron activation analysis. Arsenic was elevated tenfold and molybdenum twofold; gold, bromide, copper, iron, selenium and zinc levels were normal. Condon and Freeman [53], on the other hand, found decreased plasma zinc in uremics. As zinc content of hair, heart, liver and testes was normal, these authors ascribed the decreased plasma zinc to a redistribution phenomenon rather than to total body deficiency. Our findings differ from those described above only in that zinc content of liver and spleen was found to be increased rather than decreased or normal in uremia, The accumulation of increased quantities of cadmium and silicon in the reticuloendothelial organs in renal failure would be anticipated on the basis of decreased renal clearance of these substances. Accumulation of zinc, iron, lead and manganese is less readily explicable as these substances are primarily excreted by the intestine. Perhaps the increased content of zinc, manganese and cadmium in liver and spleen represents a redistribution phenomenon as these elements are found in high concentration in the normal kidney but are decreased in kidneys of patients with renal failure. A metalbinding protein (metallothionein) has been isolated from equine renal cortex [54]. This protein has a high affinity for both cadmium and zinc. It is likely that kidney disease is associated with a decreased amount of this important metal-binding protein and that the decreased renal cortical content of cadmium and zinc can be explained on this basis. (E) Abnormalities of major and trace elements in hypertension The decreased sodium content of liver and spleen in the non-uremic hypertensive sub-group is compatible with several descriptions of low plasma volume (and thus presumably extracellular volume) in essential hypertension [55, 561. In contrast, sodium content of kidney, liver and spleen is increased in uremia but no differences are discernible between the hypertensive and normotensive sub-groups. It has been clearly demonstrated that extracellular volume is a major determinant of hypertension in uremia [55,57] and that the majority of uremic hypertensive patients can be restored to normotension by ultrafiltration during hemodialysis [57]. Thus the lack of correlation of tissue sodium content with blood pressure in our uremic group is a somewhat surprising finding, suggesting that some factor (or factors) other than total body sodium content is a necessary concomitant to the hypertension of uremia. One such determinant may be tissue calcium content, shown in this study to be disproportionately increased in kidney and spleen of hypertensive uremics. Hypercalcemia is regularly attended by increased blood pressure [58] and calcium is known to increase vascular reactivity [59]. Weidman et al. [60] have shown that the hypertensive response to acute hypercalcemia is more pronounced in uremics than in normals.

158

SUCHATIINDRAPRASIT, GEORGE V. ALEXANDER

and HARVEYC. GONICK

There has been considerable speculation concerning the role of trace elements in hypertension. Schroeder [5] and Perry [6] have, in particular, incriminated cadmium as a potential hypertensive element. The evidence to date includes the following: (1) kidney cadmium is higher in Orientals and Americans than in Africans, correlating with the propensity for hypertension and increased industrial exposure in the first two populations [5] ; (2) kidney cadmium increases with age, suggesting accumulation due to protracted exposure; (3) rats chronically fed an increased amount of cadmium in their drinking water develop sustained hypertension [61]; (4) rats acutely injected with cadmium (intravenously, intra-arterially or intra-peritoneally) develop transient hypertension [62-641, (5) In the chronic cadmium-hypertensive rat, vascular responses to intravenously injected norepinephrine and angiotensin are diminished [65] ; similar findings have been demonstrated in vitro, employing cadmium-treated rabbit aortic strips [66, 671; (6) urine cadmium concentration is increased in essential hypertension [68], and (7) two autopsy studies, with a limited number of patients, suggested an increased cadmium concentration and cadmium/zinc ratio in kidneys of hypertensive subjects [5,69]. Schroeder has emphasized that cadmium displaces zinc from a metalbinding protein and, therefore, the tissue cadmium/zinc ratio may have greater significance than cadmium concentration alone. Injection of a zinc chelate reverses cadmium-induced hypertension in animals [lo]. In the present study we were not able to demonstrate in our hypertensive subpopulations either increased cadmium concentrations in kidney or liver or increased cadmium/zinc ratios in these organs; spleen cadmium and cadmium/zinc ratios, however, were definitely increased. It should be emphasized that the number of patients in the normal hypertensive subpopulation was small and therefore probably inadequate to confirm or deny Schroder’s postulations. Other studies have, however, produced contrary evidence. In particular, Szadkowski et al. [70] found no relationship between urinary cadmium and arterial blood pressure in a group of 169 individuals not industrially exposed to cadmium. Holden [71] has not noted an increased incidence of hypertension in 42 workers exposed to cadmium for 240 yr. Schroeder [72] has also listed a number of other trace elements which have either pressor or depressor effects when injected acutely into animals. The pressor elements included vanadium, manganese and nickel. The depressor elements included iron, cobalt, copper, zinc and chromium. Of these elements, the present study could show only decreased liver copper and decreased kidney manganese. The significance of these findings is unknown. SUMMARY

AND

CONCLUSIONS

Kidney, liver and spleen tissues from patients dying with acute renal failure, chronic renal failure and diseases not associated with kidney abnormalities (‘normals’) were analyzed for Na, K, Ca, P, Mg, Cd, Zn, Cu, Pb, Fe, Mn, Al, Si, Ti, Co, Ni, MO, Sn Cr, Sr, Ba, Li, Ag, Va and Bo. The data of the ‘normal’ group were substantially in agreement with normal values previously reported by Tipton et al. [7]. In both ‘normal’ and renal failure groups the following age relationships were noted in kidney cortex samples: (1) Cd and Zn content reached peak values in the 40-60 age interval and decreased thereafter; (2) K and P content showed a continuous decrease throughout the life span; (3) Ca content increased throughout the life span. Renal failure was associated with increased Na, Ca, and P and decreased K in most of the tissues. The

Tissue Composition

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changes in Na and K were thought to be related to inhibition of the transport enzyme, Na-K-ATPase, in uremia, whereas the changes in Ca and P were considered to be the result of secondary hyperparathyroidism. Trace elements accumulating in liver and spleen in renal failure included Cd, Zn, Fe, Pb, Mn, Al, and Si. In kidney there were increased levels of Si, Sn, and Cr but decreased levels of Cd, Zn and Mn. The increased content of Cd and Si in the reticuloendothelial organs was attributed to decreased renal clearance, as these substances are normally excreted principally by the kidney. The low levels of Cd and 2n in kidney were thought to be related to a diminution in metal-binding protein in the diseased tissues. We could find no evidence for trace element-induced kidney disease. Hypertension was found to be associated with decreased levels of sodium in liver and spleen in the ‘normal’ group. This finding was thought to be related to the decreased extracellular volume described in a segment of the essential hypertension population. In contrast, patients with chronic uremia had comparable sodium levels in hypertensive and normotensive subgroups; the distinguishing feature was an increase in calcium content of kidney and spleen in the hypertensive subgroup. The implication is that calcium may play an important role in the pathogenesis of hypertension in uremia. Trace element alterations in the ‘normal’ hypertensive subgroup included increased spleen content of Cd and Zn and an increase in the Cd/Zn ratio; Cu was decreased in liver and Mn was decreased in kidney. Although the number of samples in the ‘normal’ hypertensive subgroup was too small to permit accurate appraisal, the Cd findings are compatible with previous suggestions that Cd may play a role in essential hypertension.

Acknowledgements-The authors are greatly indebted to Mrs. Ethel Abel, R.N., a volunteer from the Kidney Foundation of Southern California, and Mrs. Helen Kocsis, R.N., who spent many hours abstracting the charts on the patients reported in this study. We are also grateful to the Department of Pathology for generously providing the tissue samples. Mr. Leon McAnulty provided technical assistance, and Mrs. Lydian Reitz and Ruby McCarty provided the secretarial assistance.

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