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Significant increase of urinary mucoprotein in environmental-cadmium-exposed Japanese subjects
~ox~co~og~Letters, 55 (I 99 1) 303-309 @ 1991 Elsevier Science Pub&hers B.V. (Biomedical Division) 0378-4274/91/$3.50 A~~~ISO378427491~9F
303
TOXLET 025 17
Significant increase of urinary mucoprotein in environmental-cadmium-exposed Japanese subjects
Teruhiko Kidol, Ryumon Honda’, Ikiko Tsuritanil, Masao Ishizakil, Yuichi Yamada’, Hideaki Nakagawal and KGji Nogawa2 ‘I>epartment of Hygiene and Public Health, Kanazawa Mediral University, Ishikawa and =Llepartment Hygiene, &hoof
of Medicine, Chiba university,
of
Chiba (.Japanj
(Received 20 January 1990) (Accepted 15 September 1990) Key words: Mucoprotein; High-molecular-weight Renal dysfunction
protein; Low-molecular-weight protein; Cadmium;
SUMMARY Urinary mucoprotein (U-MP) was determined in I69 Japanese environmental~admium-exposed and 8 i non-exposed subjects. Urinary total protein, albumin, µglobulin &-MC), cadmium (Cd) and creatinine were also measured. Significant increases in U-MP and other proteins were found in the Cdexposed subjects. Significant correlations between each protein were seen in the Cd-exposed and the total group of subjects. U-MP was highly correlated with urinary &MG and their correlation coefficient was the highest in the total group of subjects. /?r-MG was the most sensitive indicator among them to detect Cd-induced renal dysfunction, although &MG is degraded in urine with a pH less than 5.5. U-MP is an acid-soluble protein. Therefore, U-MP is also available for studies on renal dysfunction caused by exposure to Cd, in conjunction with a-MC.
INTRODUCTION
Cadmiun (Cd) exposure causes renal tubular dysfunction in the initial stage [l-3]. Low-molecular-weight (LMW) proteins such as ~~-microglobulin @-MC), at-microglobuIin and retinol-binding protein, and ~-acetyl-~-D-glucosaminidase are detected in the urine of subjects with Cd-induced renal dysfunction [4-71. In addition, highmolecular-weight (HMW) proteins such as albumin, transferrin and IgG are excreted in the urine of Cd-exposed subjects [S, 91.
Addressfor
correspondence:
da, Ishikawa, 920-02, Japan.
Dr. T. Kido, Department of Hygiene, Kanaxawa Medical University, Uchina-
67 67 67 67 67 67 67 67 67 67 67 67 67
12.1 185.6 61.2 93.6 14.9 228.6 4649 7116 4.9 1.5 50.4 123.2 3.8 -
3.14**,c 3.62**” 4.28+* 4.19*** 1.74*** 1.82*** 5..53*** 6.38*** 1.96*** 1.82*** 2.23 2.35 2.90***
102 102 102 102 102 102 102 102 102 102 102 102 102
12.1 251.7 67.5 140.0 14.9 309.2 5275 10934 4.9 10.1 55.6 122.8 4.3
G.M. 2.52+++ 2.73’** 3.40*** 3&O*** 1.70*** 1.84*** 4.66**+ 5.11*** 1.83*** 1.74*** I.92* 1.89 2.49***
S.D. 26 26 26 26 26 26 26 26 26 26 26 26 26
n
Men
6.0 68.3 25.8 29.3 6.7 75.9 124 141 2.2 2.5 42.9 Ill.1 0.2
G.M.
~
55 55 55 5.5 55
2.75 1.58 2.03 1.52 3.25
55 55
3.87
55
1.75 3.90
5.5 55
3.16 2.22
55
1.81 2.47
5.5 55
2.48
n
Women S.D.
Non-exposed subjects
“Geometric mean. bGeometric standard deviation. “Significant differences between corresponding groups of Cd-exposed and non-exposed subjects (*P
Total protein (mg/lOO ml) (mg/g cr.) Albumin (mg/l) (mgig cr.) Mucoprotein (mg/lOO ml) (mg/g cr.) Bz-MG kg/l) @g/g cr.) Cadmium &g/l) @g/g cr.) Albumin/Total protein (4g) Mucoprotein/Total protein (%) &MG/Total protein (%)
n
S.D.b
n
G.M.a
Women
Men ----
AND NON-EXPOSED SUBJECTS
Cd-exposed subjects
URINARY FINDINGS IN CADMIUM-EXPOSED
TABLE I
4.1 73.4 11.9 31.7 4.6 81.5 98 174 2.3 4.0 43.2 111.1 0.2
G.M.
2.28 2.01 3.29 2.80 2.01 1.90 3.48 3.47 1.92 1.45 1.99 1.50 2.57
SD
Urinary mucoprotein (U-MP) is a kind of acid-soluble protein which is not precipitated by most usual precipitants [IO]. U-MP is derived from the serum and the epithelium of the u~nary tract. The measurement of U-MP is relatively complicated [lo, 111, but recently a rapid and sensitive method using Coomassie Brilliant Blue G-250 has been devised [12]. U-MP has been found to be increased in malignant tumors and some renal diseases [ 131. The aim of this study is to determine U-MP in Cd-exposed and non-exposed subjects and to evaluate the significance of U-MP as an early marker to detect Cd damage, as compared with other urinary proteins. MATERIALS AND METHODS
Morning urine specimens were collected from 169 Cd-exposed subjects (67 men and 102 women), who were all over 50 years of age and lived in the Kakehashi River Basin in Ishikawa Prefecture, one of the Cd-polluted areas of Japan. They all showed Cd-induced renal tubular dysfunction and were officially recognized as ‘subjects requiring observation’ by the Research Committee organized by the Prefectural Health Authorities [ 14]. As a control, spot urine samples were collected from 8 1 non-exposed subjects (26 men and 55 women) over 50 years of age. Urinary pH was measured and neutralized when necessary. All of the samples were kept frozen at -20°C until analysis was performed. Total urinary protein was determined using the Coomassie Brilliant Blue method (Tonein-TP reagent, Otsuka Assay Co., Tokushima). Urinary albumin was analyzed by radioimmunoassay (Otsuka Assay Co., Tokushima). U-MP was measured with a U-MP kit (Otsuka Assay Co., Tokushima) [12]. Dz-MG was analyzed by enzymeimmunoassay using a kit &MC EIA kit, Fuji Rebio Co., Japan). The urinary Cd concentration was determined by graphite-furna~ atomic absorption sp~trometry using a Hitachi Model No. 180-80 equipped with an autosampling system [ 151. The values of each urinary parameter are expressed as mg or ,ug/g creatinine since the urinary condition differs in the Cd-exposed and non-exposed subjects. To determine the prevalence rates of each urinary proteinuria, the calculated 97.5% upper limits for the control population were used as cut-off levels. RESULTS
All the different kinds of urinary proteins in the Cd-exposed subjects were significantly higher than those in the non-exposed subjects (Table I). However, by comparing the proportion of each protein to total protein, only the ratio of &-MG to total protein differed significantly between the men in the Cd-exposed and non-exposed subjects and between the women in the same two groups. Prevalence rates of each type of proteinuria are shown in Table II. Expressed as mg or pg/g creatinine, the prevalence rates of every type of protein in the Cd-exposed subjects were significantly higher than those in the non-exposed subjects.
> 19 mg/l~ml 2 293 mg/gcr.
z 1193 J&l > 2096 &g cr.
3 33 B 232
3 1893 32113
Mucopratein
,&-MG 71.6*** 76.1***
7.5 52.2***
13.4 34.3*
(48,‘67) (51/67)
( 5167) (35/67)
( 9167) (23167)
10.4 ( 7/67) 49.3***~” (33167)
83.3*** (85,‘102) 84.3*** (86/102)
32.4*** (33/102) 56.9*** (58/102)
18‘6s (19/102) 31.4*** (32/102)
29.4*** (30/102) 44.1*** (45/102)
Women
0.0 (O/26) 0.0 (O/26)
0.0 (O/26) 3.8 (l/26)
3.8 (l/26) 1I .a5(3/26)
0.0 (O/26) 0.0 (O/26)
Men
Non-exposed subjects
OF CADMIUM-
1.8 (l/55) 5.5 (3/55)
1.8 (l/55) 5.5 (3/55)
3.6 (2/55) 3.6 (2155)
5.5 (3/55) 7.3 (4/55)
Women
AND /32-MICROGLOBULINURIA
aSignificant differences between corresponding groups of Cd-exposed and non-exposed subjects (*P
> 193 mgjl 2 248 mg/g cr.
2 258 2 178
Albumin
> 22 mg/l~mi 2 298 mg/gcr.
& 37 & 224
Total protein
Men
Women
Men
MUCOPROTEINURIA
Cd-exposed subjects
ALBUMINURIA,
Cut-off levels
PREVALENCE RATES OF TOTAL PROTEINURIA, EXPOSED AND NON-EXPOSED SUBJECTS
TABLE II
Bz-MG Cadmium Cadmium
Bz-MG Cadmium Mucoprotein Bz-MG Cadmium
Albumin Mucoprotein
169 169 169 169 169 169 169 169 169 169 0.850**+ 0.218*+ 0.661*** 0.671*** 0.244** 0.809*** 0.413*+* 0.300***
0XKi***
0.%6***
81 81 81 81 81 81 81 81 81 81 0.714*** 0.798*** 0.606*** 0.2.53* 0.348** 0.338** 0.166 0.716*** 0.201 0.190
r
n
I
n
250 250 250 250 250 250 250 250 250 250
n
Total
OF CADMIUM-EXPOSED,
Non-exposed subjects
PARAMETERS
Cd-exposed subjects
MATRIX BETWEEN VARIOUS BIOLOGICAL
Significant: *P
i&-MG
Total protein Total protein Total protein Total protein Albumin Albumin Albumin Mucoprotein Mucoprotein
SIMPLE CORRELATION TOTAL SUBJECTS
TABLE III
0.872+** 0.827*** 0.817*** 0.449*** 0.680*** 0.687*** 0.436*** 0.889*** 0.632*** 0.620***
r
NON-EXPOSED
AND
308
A simple correlation matrix between the various biological parameters in urine is shown in Table III. Significant correlations between each protein were seen in the Cd-exposed and total group of subjects. Urinary HMW proteins such as albumin and U-MP were also highly correlated with urinary &-MG and correlation coefficients between U-MP and Pz-MG were the highest of all in the total group of subjects (r=O.889, P
A reduced glomerular filtration rate (GFR) has been found in heavily Cd-exposed workers as well as environmental-Cd-exposed Japanese inhabitants [16]. However, pathological findings have not shown abnormal glomerular changes in Cd-exposed subjects in&ding Itai-itai disease patients [17]. On the contrary, some researchers have stressed that Cd directly leads to increased glomerular pe~eability, with albuminuria appearing due to the reduction of electrostatic restriction to polyanionic proteins [18]. In this study, proteins with a molecular weight above 40000 are defined as HMW proteins, one of which is albumin (mol. wt. 69000). U-MP is divided into 13 protein bands with molecular weights ranging from 15 000 to 230000 determined by SDS-polyacrylamide gel electrophoresis [19]. The main band of normal urine is located at 94 000 and the main band of urine of some renal diseases is at 45 000 [ 131. Therefore, most U-MP are classified as HMW proteins. U-MP of neoplasia overflows due to an increase in mucoprotein in the serum. In contrast, the increase in U-MP in renal disease such as nephrotic syndrome occurs because of an increase in glomerular membrane permeability. In the present study, increased excretion of HMW proteins such as albumin and U-MP, as well as LMW protein such as &MG, was found in the Cd-exposed subjects. U-MP has never been determined in environmental Cd-exposed subjects, in whom &-MG is the most sensitive indicator of Cd-induced renal dysfunction. However, &-MG degradation occurs when the urinary pH falls below about 5.5 [6]. UMP is an acid-soluble protein and is stable in acidic urine. In addition, compared to the correlation coefficients between each protein, U-MP was highly correlated with &MG, with their correlation coefficient the highest in the total group of subjects. Based on our results, we consider U-MP to be a useful indicator in the clarification of Cd-induced renal dysfunction, in conjunction with /32-MG. REFERENCES 1 Kjellstrom, T., (1986) Renal effects. In: L. Friberg, C.G. Elinder, T. Kjellstrijm and G.F. Nordberg (Eds.), Cadmium and Health: A Toxicological and Epidemiological Appraisal, Vol. II. Effects and Response. CRC Press, Boca Raton, FL, pp. 21-l 10. 2 Piscator, M. (1986) The nephropathy of chronic cadmium poisoning, In: EC. Foulkes (Ed.), Cadmium. Springer-Verlag, Berlin-Heidelberg-New York-Tokyo, pp. 179-194. 3 Nogawa, K. (1984) Biologic indicators of cadmium aephrotoxicity in persons with low-level cadmium exposure. Environ. Health Perspect. 54,163-169.
309 4 Saito, H., Shioji, R., Hurukawa, Y., Nagai, K., Arikawa, T., Saito, T., Sasaki, Y., Furukawa, T. and Yoshinaga, K. (1977) Cadmium-induced proximal tubular dysfunction in a cadmium-polluted area. Contr. Nephrol. 6, l-12. 5 Kido, T., Honda, R., Yamada, Y., Tsuritani, I., Ishizaki, M. and Nogawa, K. (1985) a,-Microglobulin determination in urine for the early detection of renal tubular dysfunctions caused by exposure to cadmium. Toxicol. Lett. 24, 195-201. 6 Bernard, A.M., Moreau, D. and Lauwerys, R. (1982) Comparison of retinol-binding protein and /$microglobulin determination in urine for the early detection of tubular proteinuria. Clin. Chim. Acta 126, l-7. 7 Nogawa, K., Yamada, Y., Kido, T., Honda, R., Ishizaki, M., Tsuritani, I. and Kobayashi, E. (1986) Significance of elevated urinary N-acetyl-/?-n-glucosaminidase activity in chronic cadmium poisoning. Sci. Total Environ. 53, 173-178. 8 Bernard, A.M., Buchet, J.P., Roels, H., Masson, P. and Lauwerys, R.R. (1979) Renal excretion of proteins and enzymes in workers exposed to cadmium. Eur. J. Clin. Invest. 9, 1l-22. 9 Kubota, Y, (1986) Studies of renal dysfunction among the inhabitants of a cadmium polluted area. I. Classification of urinary protein excretion patterns according to the quantitative analysis of the five proteins. Jpn. J. Hyg. 41, 539-549 (in Japanese). 10 Anderson, A.J. and Maclagen, N.F. (1955) The isolation and estimation of urinary mucoproteins. Biothem. J. 59,6388644. 11 Tamm, I. and Horsfall, F.L. (1950) Characterization and separation of an inhibitor of viral hemagglutination present in urine. Proc. Sot. Exp. Biol. Med. 74, 108-l 14. 12 Sano, K., Kanamori, K., Nakao, M., Nakajima, K. and Nakagawa, H. (1983) Study on the determination of urinary protein ~ Discrepancy between sulfosalicylic acid method and Coomassie Brilliant Blue G-250 method. Jpn. J. Clin. Pathol. 31, 174178 (in Japanese). 13 Shiba, K., Kanamori, K., Nakao, M., Shigai, T., Tomura, S., Nakajima, K. and Kodaira, T. (1984) Normal values of urinary sulfosalicylate soluble mucoprotein and its clinical significance. Jpn. J. Clin. Pathol. 32, 1372-1378 (in Japanese). 14 Ishikawa Prefecture (1984) Results of the Epidemiological Study on the Health Effects of Cadmium on the Population in the Kakehashi River Basin. Ishikawa Prefecture, Kanazawa, pp. l-56 (in Japanese). 15 Kido, T., Tsuritani, I., Honda, R., Ishizaki, M., Yamada, Y. and Nogawa, K. (1984) A direct determination of urinary cadmium by graphite-furnace atomic absorption spectrometry using the Zeeman effect. J. Kanazawa Med. Univ. 9,7%75 (in Japanese). 16 Nogawa, K., Kobayashi, E., Honda, R., Ishizaki, A., Kawano, S. and Matsuda, H. (1980) Renal dysfunctions of inhabitants in a cadmium-polluted area. Environ. Res. 23, 13-23. 17 Kitagawa, M., Miwa, A. and Murai, Y. (1983) Pathological study on twenty-seven autopsied cases with Itai-itai disease in Toyama Prefecture. Kankyo Hoken Rep. 49, 140-145 (in Japanese). 18 Bernard, A. and Lauwerys, R. (1986) Effects of cadmium exposure in humans. In: E.C. Foulkes (Ed.), Cadmium. Springer-Verlag. Berlin-Heidelberg-New York-Tokyo, pp. 135-177. 19 Shiba, K., Kanamori, K. and Harada, T. (1986) The properties of urinary sulfosalicylic acid soluble mucoproteins. Jpn. J. Clin. Pathol. 34, 195-200 (in Japanese).
303
TOXLET 025 17
Significant increase of urinary mucoprotein in environmental-cadmium-exposed Japanese subjects
Teruhiko Kidol, Ryumon Honda’, Ikiko Tsuritanil, Masao Ishizakil, Yuichi Yamada’, Hideaki Nakagawal and KGji Nogawa2 ‘I>epartment of Hygiene and Public Health, Kanazawa Mediral University, Ishikawa and =Llepartment Hygiene, &hoof
of Medicine, Chiba university,
of
Chiba (.Japanj
(Received 20 January 1990) (Accepted 15 September 1990) Key words: Mucoprotein; High-molecular-weight Renal dysfunction
protein; Low-molecular-weight protein; Cadmium;
SUMMARY Urinary mucoprotein (U-MP) was determined in I69 Japanese environmental~admium-exposed and 8 i non-exposed subjects. Urinary total protein, albumin, µglobulin &-MC), cadmium (Cd) and creatinine were also measured. Significant increases in U-MP and other proteins were found in the Cdexposed subjects. Significant correlations between each protein were seen in the Cd-exposed and the total group of subjects. U-MP was highly correlated with urinary &MG and their correlation coefficient was the highest in the total group of subjects. /?r-MG was the most sensitive indicator among them to detect Cd-induced renal dysfunction, although &MG is degraded in urine with a pH less than 5.5. U-MP is an acid-soluble protein. Therefore, U-MP is also available for studies on renal dysfunction caused by exposure to Cd, in conjunction with a-MC.
INTRODUCTION
Cadmiun (Cd) exposure causes renal tubular dysfunction in the initial stage [l-3]. Low-molecular-weight (LMW) proteins such as ~~-microglobulin @-MC), at-microglobuIin and retinol-binding protein, and ~-acetyl-~-D-glucosaminidase are detected in the urine of subjects with Cd-induced renal dysfunction [4-71. In addition, highmolecular-weight (HMW) proteins such as albumin, transferrin and IgG are excreted in the urine of Cd-exposed subjects [S, 91.
Addressfor
correspondence:
da, Ishikawa, 920-02, Japan.
Dr. T. Kido, Department of Hygiene, Kanaxawa Medical University, Uchina-
67 67 67 67 67 67 67 67 67 67 67 67 67
12.1 185.6 61.2 93.6 14.9 228.6 4649 7116 4.9 1.5 50.4 123.2 3.8 -
3.14**,c 3.62**” 4.28+* 4.19*** 1.74*** 1.82*** 5..53*** 6.38*** 1.96*** 1.82*** 2.23 2.35 2.90***
102 102 102 102 102 102 102 102 102 102 102 102 102
12.1 251.7 67.5 140.0 14.9 309.2 5275 10934 4.9 10.1 55.6 122.8 4.3
G.M. 2.52+++ 2.73’** 3.40*** 3&O*** 1.70*** 1.84*** 4.66**+ 5.11*** 1.83*** 1.74*** I.92* 1.89 2.49***
S.D. 26 26 26 26 26 26 26 26 26 26 26 26 26
n
Men
6.0 68.3 25.8 29.3 6.7 75.9 124 141 2.2 2.5 42.9 Ill.1 0.2
G.M.
~
55 55 55 5.5 55
2.75 1.58 2.03 1.52 3.25
55 55
3.87
55
1.75 3.90
5.5 55
3.16 2.22
55
1.81 2.47
5.5 55
2.48
n
Women S.D.
Non-exposed subjects
“Geometric mean. bGeometric standard deviation. “Significant differences between corresponding groups of Cd-exposed and non-exposed subjects (*P
Total protein (mg/lOO ml) (mg/g cr.) Albumin (mg/l) (mgig cr.) Mucoprotein (mg/lOO ml) (mg/g cr.) Bz-MG kg/l) @g/g cr.) Cadmium &g/l) @g/g cr.) Albumin/Total protein (4g) Mucoprotein/Total protein (%) &MG/Total protein (%)
n
S.D.b
n
G.M.a
Women
Men ----
AND NON-EXPOSED SUBJECTS
Cd-exposed subjects
URINARY FINDINGS IN CADMIUM-EXPOSED
TABLE I
4.1 73.4 11.9 31.7 4.6 81.5 98 174 2.3 4.0 43.2 111.1 0.2
G.M.
2.28 2.01 3.29 2.80 2.01 1.90 3.48 3.47 1.92 1.45 1.99 1.50 2.57
SD
Urinary mucoprotein (U-MP) is a kind of acid-soluble protein which is not precipitated by most usual precipitants [IO]. U-MP is derived from the serum and the epithelium of the u~nary tract. The measurement of U-MP is relatively complicated [lo, 111, but recently a rapid and sensitive method using Coomassie Brilliant Blue G-250 has been devised [12]. U-MP has been found to be increased in malignant tumors and some renal diseases [ 131. The aim of this study is to determine U-MP in Cd-exposed and non-exposed subjects and to evaluate the significance of U-MP as an early marker to detect Cd damage, as compared with other urinary proteins. MATERIALS AND METHODS
Morning urine specimens were collected from 169 Cd-exposed subjects (67 men and 102 women), who were all over 50 years of age and lived in the Kakehashi River Basin in Ishikawa Prefecture, one of the Cd-polluted areas of Japan. They all showed Cd-induced renal tubular dysfunction and were officially recognized as ‘subjects requiring observation’ by the Research Committee organized by the Prefectural Health Authorities [ 14]. As a control, spot urine samples were collected from 8 1 non-exposed subjects (26 men and 55 women) over 50 years of age. Urinary pH was measured and neutralized when necessary. All of the samples were kept frozen at -20°C until analysis was performed. Total urinary protein was determined using the Coomassie Brilliant Blue method (Tonein-TP reagent, Otsuka Assay Co., Tokushima). Urinary albumin was analyzed by radioimmunoassay (Otsuka Assay Co., Tokushima). U-MP was measured with a U-MP kit (Otsuka Assay Co., Tokushima) [12]. Dz-MG was analyzed by enzymeimmunoassay using a kit &MC EIA kit, Fuji Rebio Co., Japan). The urinary Cd concentration was determined by graphite-furna~ atomic absorption sp~trometry using a Hitachi Model No. 180-80 equipped with an autosampling system [ 151. The values of each urinary parameter are expressed as mg or ,ug/g creatinine since the urinary condition differs in the Cd-exposed and non-exposed subjects. To determine the prevalence rates of each urinary proteinuria, the calculated 97.5% upper limits for the control population were used as cut-off levels. RESULTS
All the different kinds of urinary proteins in the Cd-exposed subjects were significantly higher than those in the non-exposed subjects (Table I). However, by comparing the proportion of each protein to total protein, only the ratio of &-MG to total protein differed significantly between the men in the Cd-exposed and non-exposed subjects and between the women in the same two groups. Prevalence rates of each type of proteinuria are shown in Table II. Expressed as mg or pg/g creatinine, the prevalence rates of every type of protein in the Cd-exposed subjects were significantly higher than those in the non-exposed subjects.
> 19 mg/l~ml 2 293 mg/gcr.
z 1193 J&l > 2096 &g cr.
3 33 B 232
3 1893 32113
Mucopratein
,&-MG 71.6*** 76.1***
7.5 52.2***
13.4 34.3*
(48,‘67) (51/67)
( 5167) (35/67)
( 9167) (23167)
10.4 ( 7/67) 49.3***~” (33167)
83.3*** (85,‘102) 84.3*** (86/102)
32.4*** (33/102) 56.9*** (58/102)
18‘6s (19/102) 31.4*** (32/102)
29.4*** (30/102) 44.1*** (45/102)
Women
0.0 (O/26) 0.0 (O/26)
0.0 (O/26) 3.8 (l/26)
3.8 (l/26) 1I .a5(3/26)
0.0 (O/26) 0.0 (O/26)
Men
Non-exposed subjects
OF CADMIUM-
1.8 (l/55) 5.5 (3/55)
1.8 (l/55) 5.5 (3/55)
3.6 (2/55) 3.6 (2155)
5.5 (3/55) 7.3 (4/55)
Women
AND /32-MICROGLOBULINURIA
aSignificant differences between corresponding groups of Cd-exposed and non-exposed subjects (*P
> 193 mgjl 2 248 mg/g cr.
2 258 2 178
Albumin
> 22 mg/l~mi 2 298 mg/gcr.
& 37 & 224
Total protein
Men
Women
Men
MUCOPROTEINURIA
Cd-exposed subjects
ALBUMINURIA,
Cut-off levels
PREVALENCE RATES OF TOTAL PROTEINURIA, EXPOSED AND NON-EXPOSED SUBJECTS
TABLE II
Bz-MG Cadmium Cadmium
Bz-MG Cadmium Mucoprotein Bz-MG Cadmium
Albumin Mucoprotein
169 169 169 169 169 169 169 169 169 169 0.850**+ 0.218*+ 0.661*** 0.671*** 0.244** 0.809*** 0.413*+* 0.300***
0XKi***
0.%6***
81 81 81 81 81 81 81 81 81 81 0.714*** 0.798*** 0.606*** 0.2.53* 0.348** 0.338** 0.166 0.716*** 0.201 0.190
r
n
I
n
250 250 250 250 250 250 250 250 250 250
n
Total
OF CADMIUM-EXPOSED,
Non-exposed subjects
PARAMETERS
Cd-exposed subjects
MATRIX BETWEEN VARIOUS BIOLOGICAL
Significant: *P
i&-MG
Total protein Total protein Total protein Total protein Albumin Albumin Albumin Mucoprotein Mucoprotein
SIMPLE CORRELATION TOTAL SUBJECTS
TABLE III
0.872+** 0.827*** 0.817*** 0.449*** 0.680*** 0.687*** 0.436*** 0.889*** 0.632*** 0.620***
r
NON-EXPOSED
AND
308
A simple correlation matrix between the various biological parameters in urine is shown in Table III. Significant correlations between each protein were seen in the Cd-exposed and total group of subjects. Urinary HMW proteins such as albumin and U-MP were also highly correlated with urinary &-MG and correlation coefficients between U-MP and Pz-MG were the highest of all in the total group of subjects (r=O.889, P
A reduced glomerular filtration rate (GFR) has been found in heavily Cd-exposed workers as well as environmental-Cd-exposed Japanese inhabitants [16]. However, pathological findings have not shown abnormal glomerular changes in Cd-exposed subjects in&ding Itai-itai disease patients [17]. On the contrary, some researchers have stressed that Cd directly leads to increased glomerular pe~eability, with albuminuria appearing due to the reduction of electrostatic restriction to polyanionic proteins [18]. In this study, proteins with a molecular weight above 40000 are defined as HMW proteins, one of which is albumin (mol. wt. 69000). U-MP is divided into 13 protein bands with molecular weights ranging from 15 000 to 230000 determined by SDS-polyacrylamide gel electrophoresis [19]. The main band of normal urine is located at 94 000 and the main band of urine of some renal diseases is at 45 000 [ 131. Therefore, most U-MP are classified as HMW proteins. U-MP of neoplasia overflows due to an increase in mucoprotein in the serum. In contrast, the increase in U-MP in renal disease such as nephrotic syndrome occurs because of an increase in glomerular membrane permeability. In the present study, increased excretion of HMW proteins such as albumin and U-MP, as well as LMW protein such as &MG, was found in the Cd-exposed subjects. U-MP has never been determined in environmental Cd-exposed subjects, in whom &-MG is the most sensitive indicator of Cd-induced renal dysfunction. However, &-MG degradation occurs when the urinary pH falls below about 5.5 [6]. UMP is an acid-soluble protein and is stable in acidic urine. In addition, compared to the correlation coefficients between each protein, U-MP was highly correlated with &MG, with their correlation coefficient the highest in the total group of subjects. Based on our results, we consider U-MP to be a useful indicator in the clarification of Cd-induced renal dysfunction, in conjunction with /32-MG. REFERENCES 1 Kjellstrom, T., (1986) Renal effects. In: L. Friberg, C.G. Elinder, T. Kjellstrijm and G.F. Nordberg (Eds.), Cadmium and Health: A Toxicological and Epidemiological Appraisal, Vol. II. Effects and Response. CRC Press, Boca Raton, FL, pp. 21-l 10. 2 Piscator, M. (1986) The nephropathy of chronic cadmium poisoning, In: EC. Foulkes (Ed.), Cadmium. Springer-Verlag, Berlin-Heidelberg-New York-Tokyo, pp. 179-194. 3 Nogawa, K. (1984) Biologic indicators of cadmium aephrotoxicity in persons with low-level cadmium exposure. Environ. Health Perspect. 54,163-169.
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