Effect of radiothyroidectomy in chicks with emphasis on glycogen body and liver

GENERAL

AND

COMPARATIVE

Effect

of

4, 144-154

ENDOCRINOLOGY

(1%)

Radiothyroidectomy Glycogen

in ‘Chicks Body

J. G. SNEDECOR Department

of

Zoology,

University

Received

AND

of

and

Emphasis

on

Liver

D. B. KING

Massachusetts,

August

with

Amherst,

Massachusetts

14, 1963

White Rock chicks injected with 1.5 mc P/100 gm at 5 or 9 days and autopsied from 8 to 43 days later were considered severely hypothyroid by several criteria. Glycogen-body weight was reduced in one experiment but not in another. Glycogen concentration in the glycogen body was not affected. Liver weights of radiothyroidectomized birds were the same as the control, but on a per cent body weight basis the livers were significantly enlarged. Values for liver glycogen in the radiothyroidectomized birds were high and remained high in chicks fasted I& hours. Radiothyroidectomy had little effect on blood glucose or muscle glycogen. Weights of testes, combs, and spleens were definitely decreased in the hypothyroid birds, whereas the adrenal weights were similar to the controls despite the marked body weight differences.

Radioactive iodide, P3’, has been employed by Winchester et al. (1949)) Mellen and Wentworth (1962)) and Michel et al. (1962) to produce radiothyroidectomy in chicks. The same technique was used by Schlumberger (1958) in the parakeet. Although the treatment as employed by Mellen and Wentworth may not have completely blocked synthesis of thyroid hormones, the birds, nevertheless, were considered to be extremely hypothyroid on the basis of growth, feathering, gonad development, heat production, serum cholesterol, and oxygen consumption. Radiothyroidectomy was utilized in the present experiments principally to determine the effect of hypothyroidism upon the glycogen content of the glycogen body (GB). Watterson et al. (1958) were able to interfere with glycogen accumulation in the GB during the latter part of incubation by employing the decapitation-hypophysectomy technique of Fugo (1940), and they suggested that pituitary hormones may be necessary for normal accumulation of GB glycogen in the chick embryo. Treatments of post-hatching chicks with several

hormones have met with differing degrees of success (Hazelwood et al., 1962; Snedecar et al., 1963) in altering GB glycogen. Therefore, a long term depletion of a hormone under pituitary influence and known to affect blood glucose and liver glycogen levels was chosen as a valid experiment. It has been reported (Snedecor and King, 1960; Snedecor et al., 1963) that radiothyroidectomy produced no change in the concentration of GB glycogen; but very markedly increased liver glycogen. More detailed GB data are presented here as well as data on body weight and liver changes. Limited observations on testis, comb, adrenal, and spleen weights are also included. MATERIALS

AND EXPERIMENT

METHODS

1

White Rock chicks obtained from a commercial hatchery were fed normally until 4 days old. Chicks weighing between 45 and 60 gm were sorted into three groups of 10 birds each, the groups having approximately equal weight means and variability. The procedure for producing radiothyroidectomy CRT,) was that of Mellen and Wentworth 144

RADIOTHYROIDECTOMY (1962). The I’“l was administered when the birds were 9 days old, and following t,he treatment food and water were supplied ad libitum. The control birds were not injected. Birds in the third group were fed mash supplemented with iodinated casein at a concentration of 0.03%. The iodinated casein treatment was expected to simulate a hyperthyroid condition. The control and experimental groups were kept in separate cages but in the same room. All birds were fasted 18 hours before they were killed on the 13th day following the radioiodide treatment. They were taken in rotation from the three groups to equalize the effect for the groups. The birds were fasting killed by decapitation, and blood was collected for blood glucose and serum cholesterol determinations. Glucose was determined by a modification of Nelson’s (1944) method described elsewhere (Snedecor et al., 1963). The GB and samplrs of liver and leg muscle were removed, weighed, and analyzed for glycogen by methods used previously (Snedecor et nl., 1963). Total cholesterol determinations on serum were done by the method of Pearson ct al. (1953). Another sample of liver weighing approximately 0.5 gm was obtained for determination of dry weight. The sample was weighed on a torsion balance and ground on a tared watchglass with a pestle and a preweighed portion of fine sand. The ground tissue was dried for at least 24 hours at room temperature, and then in a vacuum desiccator to minimum weight. Before t,he experimental birds were killed, a surrey meter (Tracerlab W-14) was used to make a crude check on the presence of radioactivity in the thyroid region. The detector element was held at, the base of the neck, close to the normal locat,ion of the thyroids. It was assumed that any functional thyroid t,issue remaining would accumulate enough I”” to affect the Geiger element. Oxygen consumption was measured by the method of Strite and Yacowitz (1956) and the results were expressed as ml/100 gmO.“/minute as suggested by Mellen (1958) to minimize the effect of body size differences. Three birds of each group mere tested the day before autopsy and were not fasted. EXPERIMENT

2

One-day-old male White Rock chicks that weighed between 40 and 50 gm were sorted into two approximately uniform groups. Immediately after weighing, the birds were put on a low iodine diet containing thiouracil. This treatment favors maximum uptake of the radioiodide. The proce-

IN

145

CHICKS

dure for radiothyroidectomy was the same as in Experiment 1 except that the treatment was begun at an earlier age. The 39 birds which received the 1.5 me 1’31/100 gm were injected at 5 days of age. The birds were killed, 5 controls and 5 experimentals on one day, at weekly intervals beginning 8 days after the I’“’ injection. The birds were fasted from 9:00 A.M. until they were killed between 1:00 and 5:00 P.M. They mre taken alternately from the two groups. The same blood and tissue analyses were performed as in Experiment 1. In addition to checking the birds for residual thyroidal radioactivity as above, each of the controls and experimentals in the last, two groups was given a. test dose of 10 PC I’“’ 3Q hours prior to autopsy. Activity in the thyroid region was checked externally just prior to killing to assess uptake of radioiodine by any funct,ioning thyroid tissue. Resting oxygen consumption was measured in a total of 5 control and 6 RT, birds prior to autopsy on the 22nd and 29th days following II”’ treatment. RESULTS

The surveys for residual radioactivity and for ability to trap P following a test dose suggest,edstrongly that the birds were uniformly and completely “‘t,hyroidectomized” by the initial F treatment. In no case did the survey meter indicate any radioactivity significantly above background for any of the birds that received the initial dose of P a,t least 8 days before the test. Most of the II”* must have been excreted by that time, and no detectable amount was present in thyroid tissue. Of the birds which were tested for ability to trap iodine by administration of a small dose of P (Experiment 2), the controls showed activit,ies of 1600-4000 cpm above background, while none of the RT, birds showed a count significantly above background (200 cpm). The distinctly larger body weight in controls and diet.inctly higher liver glycogen values in the RT, groups substantiated the foregoing statements about the uniformity of the Iy3’ effect. A few exceptions on the basis of liver glycogen in Experiments 2 will be considered later. Oxygen consumption data are summarized in Table 1 and show clearly that oxygen utilization, independent, of body size,

146

SNEDECOR

AND

256 + 10.5 gm, which was not significantly different than the control mean. The glycogen bodies of control chicks averaged significantly above those of the RT, birds in weight. Glycogen-body weight for the IC group was intermediate and not statistically different than either of the other groups. The average glycogen concentrations were almost identical, with considerably more variability in the control group (Table 2). Blood glucose values for the control and IC groups were similar, being 201 -+ 4.5 and 196 ‘r 5.7 mg%, respectively; the value for the RT, group was 187 rt 3.1 mg%. The latter value is somewhat lower (0.03 level of significance) than the control blood glucose value. Serum cholesterols were run in duplicate on five birds from each group. The variability was great enough that, even though the averages were 134.4 + 11.2 mg% for controls and 168.9 -C 0.1 mg% for RT, birds, the difference was not significant. The IC birds averaged a distinctly lower serum cholesterol of 100.8 t 5.3 mg%, which is significantly different than the control mean at the 0.03 level. Table 2 includes values for several liver determinations. Liver weight was almost the same in birds of the t.hree groups. However, when the weights were expressed as per cent body weight, the liver weights of the RT, birds were decidedly and consistently larger.

TABLE 1 EFFECTS OR RADIOTHYROIDECTOMY AND IODINATED CASEIN FEEDING ON RESTING OXYGEN CONSUMPTION IN WHITE ROCK CHICKS F.~STED 1-3 HOURS Mean oxygen consumption (ml/100 gm o.‘5/min + SE) Chicks Control RTx Fed iodinated casein

Experiment (3)c3.51 (3) 2.39 (2) 3.64

a Age, 20 days, 12 days b Age, 4-5 weeks, 22-29 c Number in group.

la

Experiment

i 0.19 f 0.03 i. 0.10

after days

(5) 3.51 (6) 2.99

2h

f 0.10 5 0.36 -

RT,. after

RT,.

was distinctly less in the RT, birds than in the controls in both experiments. Oxygen consumption of RT;, birds, for the few tests run, was 68% of the control value in the first experiment and 85% in the second. None of the RT, birds with low liver glycogens and low liver weights (see below) in Experiment 2 happened to be included in the metabolism tests. Iodinated casein had no effect on oxygen uptake. EXPERIMENT 1 All birds in this experimental series were killed on the 13th day after P31 treatment. The average body weight of the controls, 260 -C 5.1 gm, was significantly above that of the RT, birds, 176 + 5.0 g, and there was no overlap in the weight ranges. The IC (iodinated easein-fed) group averaged

EFFECT

OF RADIOTHYROIDECTOMY GLYCOGEN BODY SND LIVER

TABLE AT 9 DAYS OF WHITE

2 AND IODINATED CASEIN FEEDING ON THE R.OCK CHICKS ST 22 DAYS OF AGE”

Control GB wt. (mg) GB glycogen (%I Total liver wt. (gm) Liver wt. as y0 body wt. Liver glycogen mg/lOO gm fresh Dry liver wt. as y0 fresh wt. a Values are means f b Significantly different “p =
wt.

SE for groups from control

27.0 32.3 7.04 2.70 99 25.84

f 5 i IL Lb rk

KING

Radiothyroidectomiaed 1.2 2.7 0.18 0.25 53 0.87

of 10 chicks. values. p = <0.05.

22.6 32.3 6.82 3.87 4706 27.22

& * + rk zk +

l.lb 1.7 0.27 O.64c 307c 0.29

Iodinated cm&-fed 24.4 31.3 6.49 2.52 166 25.82

iYc f + + i

1.1 1.6 0.28 0.15 77 I 0.22

RADIOTHYROIDECTOMY

Liver glycogen values for the control and RT, g,roups showed the greatest and moat’ cons&ent difference of the parameters measured. Fasting glycogen values for the controls averaged about l/50 the liver glycogen values for RT, birds. Mean liverglyeogen eoncentrat.ion for the IC birds was not statist’ically different than the control mean. Muscle glycogen values averaged less t,han 0.2% and were essentially the same in all groups. The distinctly lighter color of the livers of RT, birds suggested that liver lipid was increased in the RT, group (Snedecor and King, 1960). This supposition was not substant,iat,ed by the result’s of the determinations of total dry constituents of liver which would inc!ude lipid. Values for dry liver weight as per cent of fresh weight did not differ significantly between control and RT, groups. EXPERIMENT

2

Mean body weight. (Table 3) for the controls was significantly greater than that for the RT, birds at each of the six weekly determinations. Only at the second deter-

IX

CBICKS

147

mination was there a slight overlap in the weight ranges for the two groups. Figure I shows the great difference in the appearance of representatives of the two groups 6 weeks after the RT, treatment, Glycogen-body weight, as shown in Table 3, increased in both groups until the birds were 4 weeks old, and then remained essentially the same during the next 3 weeks. The means for GB weight differed statist,ically only at the fifth week after P1 treat,ment, at which time the control glycogen-body average was higher. Glycogen-body glycogen concentrat,ion (Table 3) did not differ significantly between control and RT, groups at, any of the weekly periods. There was a fall in per cent glycogen aft,er about 40 days of age which occurred in hot12 groups. Blood glucose in the control birds averaged higher t,han in the RT, birds in ail groups except t,he final one, but the difference was significant only at the second week after I’“’ treatment. (See Table 3). Liver changes both in absolute weight and as per cent body weight are presented in Table 3. Although the means for abso-

FIG. 1. Control and radiothyroidectomized White Rock male chicks. The effect of the treatment somewhat exaggerated since the largest control and smallest RT, bird of their group are pictured. body weights are 900 and 300 gm, respectively, 6 weeks after RT, at 5 da.ys of age.

is The

wt.

glycogen

(mg)

(gm)

(fig)

glycogen gm)

Leg muscle (md100

gm)

wt.

Controls RT,

Controls RT, Controls RTx RT,”

Controls RTx Controls RTx RTxb

Controls RTx Controls RT, Controls RT, Controls RTx Controls RTx

3.354 4.176 2.52 4.40 4.63 (3.46) 26.01 28.67 132 4169 5131 (319) 131 166

122 95 18.8 19.2 4797 5008 24.16 24.80 182 168

0.34 1.02 79 1019 434

0.208 0.227 0.07 0.25 0.13

6 10 1.3 1.2 324 4G0 1.13 1.57 6 9

f 31 % 24

i + % + +

_+ + + f IL

& rt + + -t + i% + +

8

OF RADIOTHYROIDECTOMY MUSCLE

a Values are means + SE for groups of five birds. b The means and SE of preceding group after removal of SE.

(mg/lOO

wt. as O/e wet

(my%)

Glycogen

Dry

wt.

km)

Liver wt.

% Body

glucose

Blood

y. Glycogen

Total

GB wt.

Body

EFFECT

of the

F * f %

k + + *

f f + k i * rt + + %

0.53 0.13 35 370

one very

& + rt If:

ct % -f % + + + % % F

22

(in parentheses

180 5 8 99 % 11

0.60 0.33 86 372

0.471 0.741 0.08 0.31

22 16 2.0 1.5 489 388 2.00 0.45 6 16

i f f f %

+ + * % +

% f rt f f + f f zk +

0.59 1.14 258 900 790

2.282 1.401 0.04 0.45 0.32

below)

BLOOD

in the group.

131 + 24 170 % 11

(158)

11.167 11.314 2.35 4.00 4.40 (2.48) 26.52 26.56 474 2784 3441

485 283 26.0 23.5 6289 5749 24.58 24.73 161 151

29 39 15 5.4 4.3 356 722 1.03 0.84 10 6

GLYCOGEN BODY, ROCK CHICKS”

Days after 11~1administration

26.71 % 27.94 % 844 ct 3733 %

9.071 8.143 2.60 4.16

351 198 26.6 28.9 6192 6651 23.41 23.03 168 159

low value

0.282 0.728 0.23 0.33

7 10 2.7 2.5 568 656 0.81 0.89 3 4

YO + 17 172 * 15

25.47 27.07 169 4676

5.841 5.822 2.97 4.10

197 141 21.9 18.3 4980 4986 23.00 25.55 184 170

15

TABLE 3 AT 5 DAYS ON BODY WEIGHT, GLYCOGEN, AND LIVER OF WHITE

See text

11.983 12.673 1.99 4.12 4.32 (2.91) 27.13 27.18 402 4061 4842 (941) 92 85

603 308 30.0 24.6 6466 4585 21.33 18.57 167 154

for

comment.

0.49 0.55 171 1057 920

0.583 1.351 0.12 0.45 0.32

35 23 4.5 3.0 1091 619 1.02 0.27 4 4

k 25 % 23

-t + % 5 rt

f + k rt rt

f f * If: i rt % + rt f

36

GLUCOSE,

0.23 0.78 57 729 259

1.013 1.841 0.15 0.32 0.20

24 42 3.7 3.6 882 560 0.91 0.89 11 5

Note

reduction

100 % 14 78 + 24

F + f f +

f f + f f

% % f f + f f f + +

(616)

18.500 17.112 2.14 3.97 4.32 (2.55) 26.82 27.19 181 3416 4108

870 479 28.7 33.3 6082 7125 20.97 21.79 157 164

43

RADIOTHYROIDECTOMY

lute liver weight in t,he control and RT, groups did not differ significantly at any phase of the experiment, the means for liver weight as per cent body weight for the two groups differed significantly at each determination. As in Experiment 1, the livers of the R.T, birds were larger in relat,ion to body weight than the control livers. Again, as in Experiment, 1, liver glycogen values averaged much higher in the RT, birds. Fasting in this experiment was of shorter duration, and the control glycogen values were accordingly higher. Values for RT, birds were not quite as high as in the younger, longer fasted animals of Experiment 1. In four cases the liver glycogen value among the 30 birds of the RT, groups was less than l%, whereas in the remainder of cases it was usually above 3.4% (only 3 between 1.2 and 3.4%). Concomitantly, in these cases of low glycogen which were in the control range, liver weight expressed as per cent body weight was also more like that of t#he control groups (Fig. 3). However, the four birds were not distinguishable from other birds in their respective groups on the basis of body weight or any

I z z

IN

148

CHICKS

of the ot,l:er criteria measured. The effect on t,he means and deviations produced by the removal of the low liver weight and glycogen values from their respective groups is shown in Table 3. The validity of this adjustment is considered in the tfiscussion section. Muscle glycogen values shown in Table 3 were not consistently different in the eontrol and RT, birds. The values showed considerable variation, and no statistical differences were demonstrated. Figure 2 shows the pattern of Cilailge in serum eholest,erol during the experimenta,l period. Higher initial values were followed by a decline to a lower level; t,he mean values for the RT, groups were sign%cantly above the control means except at 27 days after R?,. Thirty-six and 43 days after the Ii,” injection, the gonad weight, means were definitely smaller for the RT, groups, and t,he combs of RT, birds were very much smaller than those of the controls. The weights of adrenals of RT, and control chicks were not statistically different at either age. The spleens of RT, birds were smaller at the two ages, ancl were most

100 0 CONTROL a RTx

AGE

IN

DAYS

FIG. 2. Serum cholesterol values for control and radiothyroidectomized from 15 to 43 days after P administration in Experiment 2.

White

Rock

male

chicks

150

SNEDECOR

AND

KING

5000

2500 0 0

1000

ol 8 g

00

l a

500 0 0

Y s

0 0

0

250

. 0

0 0

ooo

5 o&o

3 3 0

0

0

0

100

0 0

0

50

0 0

25 0 CONTROL l RTx 0

~~-1

2 LIVER

3

4

5

6

WT. AS % BODY WT.

FIG. 3. Semilog plot of liver weight as T-/o body weight VS. liver glycogen concentration. The widely fluctuating glycogen values for the briefly fasted control birds is in contrast to the uniformly high liver glyeogens of the RT, animals. The cases in which RTX birds had low liver glycogens and low liver weight as per cent body weight are evident among the plotted values for the controls.

EFFECT

TABLE 4 OF RADIOTHYROIDECTOMY ON WEIGHT OF COMB, TESTES, AND SPLEEN OF ~-DAY-OLD WHITE ROCK CHICKSQ Days after trentment

Group

Untreated

3G

Radiothyroidectomized

43 36 43

a Values

are means

f

112’

SE for groups

Weight Comb

518 545 48 59 of 5 birds.

I f * +

Testes

120 31 6 12

205 400 120 140

* 29 * 93 * 17 i 31

ADRENALS,

(mg)

Adrenals 70 89 76 85

i I tf

8 7 6 12

Spleen 924 1953 331 419

& & & -t

116 90 41 7-I

RADIOTHYROIDECTOMY

noticeable in the oldest birds. The weight data for these organs are summarized in Table 4. DISCUSSIO?;

Mellen and Went,worth (1962) concluded that their method for thyroid destruction in young chickens with P might not be i s effect,ive as surgica’l thyroidectomy beause they were able to demonst,rate that ;”thyroid hormones were being formed in RT, birds. Taurog et al. (1960) found that ihyroxine-I’“’ could not be detected in the iver or plasma of completely thyroidec11 $omized rats after administration of a test dose of P, whereas in similarly treated RT, rats significant amounts of tagged hormone were present. A critical comparison Cf the effects of surgical and radiothyroidectomy has not, been made for the chick. In the work of Mellen and Wentworth (1962) and in the present RT, experiments, the chicks were certainly in a very hypothyroid condit.ion. The marked differences bet,ween control and RT, birds in body weight., appearance, oxygen consumption, and serum cholesterol were comparable in the two experiments. As previously reported (Snedecor et al., 1963) radiothyroidectomy failed to alter the glycogen concentration of the GB. Glycogen-body weight and therefore total GE glycogen were not. depressed significantly by t,he RT, treatment- in the second *experiment, although GB weight was significantly less in the first experiment. Evidently, GB growth and glycogen accug@ation are not consistently influenced by tihe lack of thyroid hormone. Age changes in the GBs of controls in Experiment 2 compared well with the ‘Tames for GB weight, glycogen concentral ion, and t.ot,al glycogen present,ed earlier @nedeeor et al., 1963), except that there was no peak in glycogen concentration at 3 weeks of age in the present experiment .nd the maximum t,ot,al glycogen values %vere somewhat lower t’han previously. The effect of thyroidectomy on liver glycogen has been recorded in detail very infrequently in the literature. The most

IN

CHICKS

151

extensive work involving birds is that of Riddle and Opdyke (1947), who reported that the fasting (24 hoursj liver glycogen of surgically thyroidectomized pigeons was about three t,imes as high as in fasted controls and half as great as in nonfasted controls. Values for nonfasted thyroidectomized pigeons were not given. The high fasting glycogen levels in the RT, chicks in the present experiment were in sharl, contrast to the low values for the fasted controls. From the results in Experiment I it was apparent, that in RT, birds not only was the liver glycogen high, but the glycogen was not utilized extensively during an l&hour fast. The briefly fasted birds of Experiment 2 also exhibited high liver glycogens, which indicated that the high level in RT, birds was not a consequence of fasting but resulted from glycogen accumulation prior to fasting. Benoit (1936, 1937a) noted enlargement of t.he liver in the thyroidectomized Pckin duck. Combined data from three papers for 21 controls and 28 thyroidectomized animals show liver weight as per cent body weight to be 2.2% (1.63.2%)) for controis and 3.870 (2.1-6.370’) for operated animals. These values compare very well with t!Ic values reported here, especially for t)he larger birds of Experiment. 2. BenoitPs ducks were 3-5 months old and weighed between 1500 and 3030 gm. The autopsies were at 19-61 days after thyroidectomy, and there was evidently no marked change in body weight following the operation. High liver glycogen and high relative liver weight seem to be charact,erist.ic of thyroidectomized animals. Recall that, in Experiment 2 there were four cases among the RT, chicks where both relative liver weight and liver glycogen were in the control range. The distinct difference of the four aberrant cases from the remainder o.! the RT, birds in the two respects suggested the possibility that the four bird8 were less completely thyroidectomized than the others. If so, it could mean that liver glycogen and liver weight as per cent body weight are more sensitive indicators of completeness of thyroidectomy than are

152

SNEDECOR

body weight and serum cholesterol. It is also possible that the liver changes represent the first indication of recovery of thyroid function in thyroid tissue s&iciently damaged at first to make the animals temporarily athyreotic. The occurrence of aberrant cases chiefly in the later groups fits this proposal. A relationship between liver weight and glycogen content in livers of rats and cats treated experimentally only to alter liver glycogen was found to depend upon the fact that the deposition of glycogen in the liver was accompanied by a proportional addition of water (Fenn, 1939; Fenn and Haege, 1940). When liver glycogen was experimentally increased, for example, by glucose administration, water was stored and increased the absolute liver weight as well as liver weight as per cent body weight. Although it is likely that water storage accompanies the high glycogen concentration in RT, chicks, the larger relative liver weights of the RT, animals cannot be wholly accounted for on this basis unless the proportion of water to glycogen stored is considerably greater than the 2.3 gm of water per gram of glycogen calculated by Fenn (1939) for the rat. If glycogen and the water which accompanies it were to account entirely for the difference in liver weight as per cent body weight, between normal and RT, birds, then our calculations indicate that the ratio of water to glycogen would have to be above 5: 1. However, the few data we have for per cent water in essentially normal livers of widely varying glycogen concentration do not indicate a ratio above 2.8 to 1. These observations sugg,est that glycogen and water storage only partially account for the difference in relative liver weight betwen RT, and control animals. In addition, determinations of lipid and protein are needed for a valid int,erpretation. In the discussion above, considerable emphasis has been placed on the ratio, liver weight as per cent body weight. Burger et al. (1962) rightly criticized the practice of expressing organ weight as per

AND

KING

cent body weight except when the relationA ship can be shown to have real validity/ Linear regressions of liver weight on bod$ weight calculat’ed for both the control anq the RT, data had their intercept approxi+ mately at the origin. Covariance analysis’ (Snedecor, 1956) showed that the regres4 sion for the values from the RT, group either with or without the four aberran values for liver weight, was not paralle i (F = 43) to the regression based on thd control data. These findings seem to justif these conclusions : (1) In this experimen 1 the liver weight: body weight ratio is valid expression; and (2) the liver weight: body weight ratios for the RT, and contra ” birds are significantly different. No linear relationships for organ weight: body weight were established for GB, tes 1 tes, adrenal, spleen, or comb; therefore, th weights for those structures have not bee d expressed as per cent body weight. Measurements of liver dry weight indicated no major change in total liver solids, and this would argue against any markeq change in total liver lipid. Benoit (1936) on the other hand, reported a fourfol c/ increase in total liver lipid in the duck following thyroidectomy, but Riddle an Opdyke (1947) found less lipid in th livers of fasted thyroidectomized pigeon than in livers of fasted controls. Turne 1 (1960) stated that thyroidectomy in mammals resulted in higher liver glycogen but no increase in liver fat. Clarification of th effect of thyroid hormone deficiedcy on,7 liver lipids of various species is needed. If thyroidectomy is done during thy rapid growth phase, body weight is greatly’ affected. The smallest group mean for RT; birds in Experiment 2 was 52% of the con trol average, but Simmons (1943) reporte that average body weights at 40 days wer j 25% of the control for birds thyroidectoj mized before 10 days of age and 50% of th control when the operation was Blivaiss (1947) thyroidectomized Brow Leghorns at 10 days of age and recorde body weights at 66% of the controls at month, 70% at 2 months, and 52% at months. The data of Mellen

RADIOTI-IYROIDECTOMY

&orth (1.962) showed that growth in different strains of c.hicks was affected somei *hat different,ly by radiothyroidectomy. heir data for birds of a Rhode Island Red F1nd White Leghorn cross, at 4 and 7 weeks of age, compare quite well with the ody weights recorded in this report. The Pesults of surgical thyroidectomy by Simmons (1943) and Morris (1951) are in ‘ greement with the present RT, results and how a markedly smaller comb weight, *educed testis weight, and adrenals with i+ssentially the same weight. as in controls. Riddle and Opdyke (1947) reported that asting blood sugars of thyroidectomized 1 irds were not significantly different t.han c.ontrols. The results of the present experi1 rjnent suggest that RT, birds, both fasted fnc? unfasted, have a slightly lower blood gugar than the controls. The serum cholesterol values reported by Mellen and Wentworth (1962) for RT, and 1ontrol chicks at. 44 days of age are some1 hat higher than our values, but t.he dat.a indicate about the same relat.ive degree of r” hypercholesteremia in the RT, birds. Michel et al. (1962) observed hypercholes$eremia in RT, chicks and reported values essentially the same as ours for the group I adiothyroidectomized for 43 days. The 1i igh cholesterol values in both control and ET, birds for the 15 and 22-day post$reatment groups in Experiment 2 remain unexplained. The values from Experiment 1 for approximately the same time after RT, are much lower. Since al1 the cholesterol determinations were done in a 2-day period, variations because of reagent 01 procedural differences do not seem likely. One clue is that the serum blanks were high in those samples showing unusually high cholesterols, which indicat,es that there was some difference in the serum samples in addition to t,he higher cholesterol. The dat,a on oxygen consumption of both control and RT, birds at 3 weeks of age closely with the resu1t.s reported by and Wentworth (1962). RT, the oxygen consumption of t.he birds to a Iesser extent. The ;hicks in Experiment 1 that had been fed

IS

153

CHICKS

consumed oxygen at iodinated casein almost the same rate as t.he ~ontr&; according to the findings of Mellen (19581, that would be the expected result because, in his experiment, the effect of iodinated casein did not persist, for as long as 18 hours after the intake was stopped. Thus, the fasted IC birds might be expected t’o rat.es similar to the have metabolic controls.

The authors are grateful to Dr. W. J. Mellen, Poultry Department, ~niuersity of Massachusetts, for radiothyroidectomizing the chicks and providing animal facilit.ies for this project. We also express appreciat,ion to George Ghareeb, Marilyn Moses, and Miltlred lSnedecor for technical assistance. This investigation was supported by Public Health Service Research grant A-1266 from the National Institute of Arthritis and Metahoiie Diseases. REFEREKCES

BCNOIT, J. (1936).

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