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Gonadotropin levels in sera and pituitary glands of female rats treated with alloxan
P~rgamon Press
Life Silences Vol. 14, pp . 289-296, 1974. Printed in Grit &iteia
GONAD0IROPIN LEVELS IN SERA AND PITUITARY GLANDS OF FEMALE RATS TREATED WITH ALLOXAN Borden E . Rowland and Edward J . Zebrowski Department of Oral Biology, The University of Manitoba, Winnipeg, Manitoba, R3E OW3, Canada (Received 6 September 1973 ; in ânai form 26 November 1973) SUMMARY
Alloxan awnohydraxe in saline solution was injected intraperitoneally into .ywuWg -(35-8Wy -01d) and older (95 day old) femme rats at dose levels of 7 .5 vg or 15 .0 ng/100 g of body wt . In both age groups of rats, only the high dose of alloxan was effective to produce peruanent diabetes as judged by the presence of hyperglycemia and glucos uria . The rats were bled by cardiac puncture and autopsied 21 days following the alloxan treatment . In young rats, diabetes resulted in a significant reduction in body weight gain and in ovarian and anterior pituitary weights . Seren and pituitary LH levels of these young diabetics were, respectively, significantly lower and essentially the sane, whereas their serum and pituitary FSH levels were, respectively, essentially the same and significantly higher than those of the controls . In the older diabetics, although a significant decrease in body weight gain was observed, the ovarian and pituitary wei~ts as well as the serum and pituitary gonadotropin levels were essentially the same as compared to the controls . Experiments with alloxan-diabetic rats have demonstrated the detrimental effects on reproduction brought about by a deficiency of insulin .
Irregular
and prolonged estrous cycles are often characteristic of diabetic rats (1,2) . Complete cess.atian of estrous cycles in diabetic rats has also been reported (3,4,5) .
When young female rats were treated with alloxan the ovaries atro-
phied and were found to contain only follicles (6) .
Liu et al . (7) have re-
ported regression in ovarian weights of immature rats treated with alloxan . The adverse effects of diabetes on reproduction could be due to reduced ovarian responsiveness to gonadotropins . experiments of Farina et al .
This mechanism is suggested by the
(8) and Liu et al .
(7) .
These reports however
disagree with the earlier findings of Shipley and parley (3) .
Diabetes may
also impair gonadotropin secretion as suggested by the experiments with parabiotic rats reported by Shipley (6) .
In experiments with male rats reduced 289
290
Alloxan Diabetes end Gonadotropin Secretion
Vol . 14, No, 2
serum levels of both follicle stimulating hormone (FSH) and luteinizing hormoms (~) have been demonstrated 8 days following alloxan treatment (9) .
In
mature females however, no reduction in serum levels of either gonadotropin was found 7 days after alloxan treatment (7) . In the following experiments, the effect of alloxan treatment on ovarian weights and on pituitary and serum levels of FSH and IH in female rats of two ages was determined . MATERIALS AND METHODS Tlvo experiments were conducted using female Sprague-Dawley rats from our own colony .
In the first experiment the rats were 35 days old while in the
second experiment the rats were 95 days old when the treatment was initiated . The animals were maintained in individual cages in a light (12 hr light, 12 hr dark) and temperature (74 ± 1 °F) controlled room and received Purina Lab Q~ow and distilled water ad libitum .
In each experiment the animals were ass-
igned to treatment groups, allowed several days to become accustomed to the individual cages and then fasted for 24 hours .
At the end of the fasting per-
iod the treated animals were injected intraperitoneally with alloxan monohydrate dissolved in 0 .9$ saline at doses of 15 mg/100 g body weight (high dose) or 7 .5 m8/100 g body weight (low dose) .
The low dose of alloxan was included
to determine if a sub-diabetogenic dose of the drug would affect any of the characteristics studied .
Urine glucose levels were determined daily using
Tes Tape (Eli Lilly F, Co .) .
Rats receiving the high dose of alloxan showed
urine glucose levels of at least 2 percent throughout the 21-day experimental period .
Although most of the rats receiving the low dose of elloxan initially
showed measurable glucose in the urine, by day 21, with the exception of one or two animals in each experiment, the urine glucose tests were negative and the animals showed no other evidence of diabetes . In the horning an day 21 and following a 16-hr fast, the rats were anesthetized with ether and blood samples were obtained by heart puncture . animals were then killed and anterior pituitaries and ovaries were removed
The
Vol. 14, No . 2 and weighed .
Alloxan Diabetes and Gonedotropin Secretion
291
Sera and pituitary glands were frozen until assayed for glucose
and gonadotropins .
Serum glucose levels were determined by a glucose oxidase
method (Glucostat, Worthington Biochemical Corp .) .
The concentration of LH
in pituitary homogenates and sera was determined using the ovine-ovine radioimmunoassay described by Niswender et al . (10) . rat-LH-RP-1 .
The standard used was NIAMD
A similar double antibody radioismtmoassay distributed by the
National Institute of Arthritis and Metabolic Diseases, NIH, was used to measure FSH concentration .
Data for FSH were expressed in terse of NIAMD rat-FSH-
RP-1 . The significance of differences between treatment groups were determined by Duncan's Multiple Range Test (11) . RESULTS The effects of alloxan-treatment in 35-day old rats are shown in Table 1 . the low dose of alloxan did not affect any of the characteristics studied with the exception of serum glucose concentration .
Serum glucose was slightly,
but significantly elevated in the low dose rats as compared to controls .
The
rats receiving the high dose of alloxan had significantly lower body weight gains during the experimental period than did the control rats .
Rats on the
high dose also had significantly lower pituitary and ovarian weights than did either control rats or those receiving the low dose of alloxan.
The serud
glucose level was significantly elevated in rats on the high dose when compared with either of the other groups .
Although no differences were detected
in pituitary concentration of W, the serum level of this hormone in rats receiving the high dose was reduced to approximately half that observed in control rats or rats receiving the low dose of alloxan .
In contrast to LH, the
pituitary concentration of FSH was elevated in rats receiving the high dose of alloxan, but the serum levels of this hormone did not differ significantly between groups . the results of the second expérinent in which older animals were studied are s++~+~+ zed in Table 2 .
As noted in the younger animals, the low dose
Vol : 14, No . 2
Alloxan Diabetes and Gonadotmpin Secretion
292
TABIE 1 Effect of Alloxan Treatment on Body Weight Gain, Organ Weights, Serum Glucose Concentration and Gonadotropin Levels in Young * Female Rats . Alloxan treatment High dose Characteristic Control Low dose + Number of rats
6
7
9
228 227 t 6 t ± 6 Body weight (g) Body weight gain (g)
74 ± 3a
181 ± 10
68 ± 5a'b
Serum lucose conc . (mg/lÔ0 ml)
75 .7 ± 2 .2 a
Ovarian weight (mg)
85 ± 2a
88 ± 7a
8 .9 ± 0 .9a
9 .3 ± 0 .6a
Pituitary weight (mg)
49 ± lOb
b
90 .6 t 2 .8
324 .8 ± 31 .2 59 + 7b 6 .4 ± 0 .5b
Pituitary Lfi conc . (ug/mg)
1g .5 t 1 .5
18 .7 t 2 .1
20 .1 ± 1 .9
Pituitary FSH conc . (ug/mg)
2 .60 ± 0 .22a
2 .41 ± 0 .17a
4 .11 ± 0 .48b
Serum LH conc . (ng/ml)
62 .5 ± 8 .2a
63 .6 ± 11 .7a
32 .5 t 4 .2 b
Serum FSH conc . (ng/ml)
231 t 24
232 ± 22
c
245 t 18
35 days old at time of alloxan injection . + Low dose = 7 .5 mg/100 g body weight, high dose weight .
15 mg/100 g body
tMean t S .E . a ' b ' cMeans with different superscripts are significantly different (P<0 .05) .
of alloxan was ineffective in altering the characteristics studied .
the rats
receiving the high dose of allozan had significantly reduced body weight gains and elevated saran glucose levels,
the reduced ovarian and pituitary weight
noted in the younger diabetic rats did not occur in the old diabetic rats . addition, treatment effects on neither pituitary nor serum levels of FSH or
In
293
Alloxen Diabetes and Gonadotropin Secretion
Vol . 14, No . 2
TABLE 2 Effect of Alloxan Treatment on Body IYeigktt Gain, Organ Weights, Serum Glucose Concentration and Gonadotropin Levels in Old' Fessle Rats . Alloxan trcatment Characteristic
Control
Number of rats
12
Body weight (g) Body weight gain (g)
280 ± 6t
Low dose +
High dose
9
11
289 t 8
258 ± 10
25 t 3 $
23 t 5 a
-3 t 6b
Serum glucose conc . (mg/100 ml)
118 t 5 a
151 t 36 a
400 t 51b
Ovarian weight (mg)
78 ± 3
87 1 5
ß2 t 6
Pituitary weight (Ag)
14 .6 f 0 .5
14 .2 t 0 .9
13 .1 ± 0 .7
Pituitary LH conc . (ug/mg)
10 .1 ± 1 .2
12 .9 t 1 .7
10 .2 t 1 .6
Pituitary FSH cons . (Vg/=g)
1 .54 ± 0 .06
1 .59 t 0 .10
1 .70 t 0 .20
Serum LH conc . (ng/ml)
32 .7 t 2 .0
36 .6 t 2 .5
Serum FSH conc . (ng/ml)
255 3 23
244 ± 30
t
~
30 .2 ± 3 .2 285 t 28
95 days old at time of alloxan injection
+ Low dose = 7 .5 mg/100 g body weight ; high dosa ~ 15 mg/100 g body weight . ' t ldean ± S .E . a,b~~s
with different superscripts are significantly different (P<0 .05) .
W ware found . DISCUSSION the results of the present experinants demonstrate that in spite of the numerous toxic effects of the drug (12}, a sub-diabetogenic dose of alloxan produced no lasting effects on gonadotropin secsetion in the feaale rat .
It
Alloxaa Diabetes and Gonadotropin Secretion
294
Vol . 14, No. 2
is possible that pituitary and seras levels of gonadotropins had been affected following injection of the drug but that recovery had occurred by the end of the 21-day period .
Previous work with male rats using a higher dose (15
mB/100 g body weight) indicated that pituitary and serum levels of both gonadotropins were depressed at 8 days after injection of alloxan (9) . The animals receiving the high dose of alloxan in each of the experiments were considered to be diabetic as indicated by urine and serum glucose levels as well as body weight changes .
It was presumed that these animals
were not showing morsel estrous cycles, although we have no data to confirm that assusption,
there are numerous reports of prolonged estrous cycles or
complete absence of estrous cycles in diabetic rats (1,2,3,4,5) .
In the pre-
sent study the young diabetic rats showed reduced ovarian weights as has been reported by others (5,6,7) . not alter ovarian weight .
In the old rats, however, alloxan treatment did the gross appearance of some of the ovaries from
diabetic rats of both ages differed fros normal ovaries due to the presence of large, pale corpora tutee .
This observation suggests that diabetes result-
ed in prolonged maintenance of corpora lutes and therefore ovarian weight was probably not a good measure of ovarian activity in diabetics of either age . Lawrence and Contopoulos (5) reported persistent corpora lutes in rats treated with alloxan at 40 days of age and autopsied 62 days later .
17îe ovaries
in their diabetic rats were below normal in size . 11îe pituitary and serum gonadotropin assays provide evidence that gonadotropin secretion had been affected by diabetes in the young rats .
The
reduced basal levels of LH could have been responsible for the reduction in ovarian weight .
Since there was no increased storage of hormone in the pit-
uitary gland it must be assumed that both synthesis and release of hormone had been reduced . betic rats .
The pituitary levels of FSH were elevated in the young dia-
This effect is difficult to interpret since serum levels of FSH
were not affected by treatment .
The mechanism whereby alloxan induced dia-
betes codifies pituitary gonadotropin synthesis and release remains to be
Vol . 14, No. 2 investigated .
295
Allo :aa Diabetes and C,ooadotcopin Secretion
It is of interest to note that the treatsent effects on gona-
dotropins in young rats i .e ., reduced serim LH levels without changes in pituitary LH and elevated pituitary FSH levels without changes in soma FSH, have been reported in fes+sle rats that were underfed (13) .
These effects app-
ear to be aore . eaaily produced by underfeeding than by rendering animals diabetic and even occur in old rats (13) .
This is probably explained by the
fact that underfeeding is a more severe metabolic stress than diabetes as indicated by body weight changes .
Underfed rats show considerable weight loss-
es (13) while the diabetic rats in this study either asintained their starting body weight or actually showed a slaved rate of growth .
Although the cal-
oric intake is greater than normal in diabetic rats (14) and less than noroel in underfed rats, the effects at the cellular level in the hypothalamus and/ or pituitary gland, as reflected by changes in ganadotropin levels, appear to be similar . ACIWOIiIBD(;BNEriTS The authors are grateful to Dr . G .D . Niswender, Dr . L .E . Reichert, Jr ., and the National Institute of Arthritis and Metabolic Diseases, Rat Pituitary Hormone Prograa for providing the materials used in the radioiasamoassays . This study was supported by grants MA-4454 and !dA-3627 from the Dbdical Research Council of Canada . REFERENCES 1.
M .E . RAVIS, N .K . FUGO and X . G . 1 .AlIRENCE, Proc . Soc . Exp . Biol . Med . 66, 638-641 (1947) .
2.
J .E . LEVI and T . IIEINBERG, Proc . Soc . Exp . Biol . lied . 72, 658-662 (1949) .
3.
E .G . SHIPLEY and K .S . DANLEY, Aver . J . Physiol . 150, 84-94 (1947) .
4.
J .A . SINDEN and B .B . LONGt1ELL, Proc . Soc . Exp . Biol . Med . (1949) .
5.
A .M . LAIIRBNCB and A .N . CONTOPOULOS, Acta Endocrinol . 33, 175-184 (1960) .
6.
E .G . SHIPLEY,'~te Use of Alloxan in the Production of M abetea Mellitus", Ph .D . Thesis, Univ . Iliac . Library (1944) .
7.
F .T .Y . LIU, H .S . LIN and D .C . JOHNSON, Endocrinology 91j 1172-1179 (1972) .
70, 607+610
296
Alloxan Diabetes and Goaadotropin Secretion
Vol, 14, No, 2
8.
J .M .S . FARINA, R . A . CHIERI, J .C . HASABE and V .G . FOGLIA, Fert . Steril . 22, 794-798 (1971) .
9.
B .E . HOWLAND and E .J . ZEBROWSKI, J . Rs~rod . - Fart .- 31, 115-118 (1972) .
10 .
G .D . NISWENDER, A .R . MIDGLEY, JR ., S .E . MONROE and L .E . REICHERT, JR ., Proc . - Soc . Ex~ Biol . Med . 128, 807-811 (1968) .
11 .
R .G .D . STEELS and J .H . TORRIE, Princi les and Procedures of Statistics, McGrsw-Hill Book Company, Inc ., N . ,
12 .
C .C . RERUP, Pharaacol . Rev . 22, 485-518 (1970) .
13 .
B .E . HOWLAND, J
14 .
E .J . ZEBRAWSKI and N .S . RAMAMURTHY, Internat . Assoc . Dent . Res , abstract +514 (1972) .
Ra-prod . Fert . 27, 467-470 (1971) .
Life Silences Vol. 14, pp . 289-296, 1974. Printed in Grit &iteia
GONAD0IROPIN LEVELS IN SERA AND PITUITARY GLANDS OF FEMALE RATS TREATED WITH ALLOXAN Borden E . Rowland and Edward J . Zebrowski Department of Oral Biology, The University of Manitoba, Winnipeg, Manitoba, R3E OW3, Canada (Received 6 September 1973 ; in ânai form 26 November 1973) SUMMARY
Alloxan awnohydraxe in saline solution was injected intraperitoneally into .ywuWg -(35-8Wy -01d) and older (95 day old) femme rats at dose levels of 7 .5 vg or 15 .0 ng/100 g of body wt . In both age groups of rats, only the high dose of alloxan was effective to produce peruanent diabetes as judged by the presence of hyperglycemia and glucos uria . The rats were bled by cardiac puncture and autopsied 21 days following the alloxan treatment . In young rats, diabetes resulted in a significant reduction in body weight gain and in ovarian and anterior pituitary weights . Seren and pituitary LH levels of these young diabetics were, respectively, significantly lower and essentially the sane, whereas their serum and pituitary FSH levels were, respectively, essentially the same and significantly higher than those of the controls . In the older diabetics, although a significant decrease in body weight gain was observed, the ovarian and pituitary wei~ts as well as the serum and pituitary gonadotropin levels were essentially the same as compared to the controls . Experiments with alloxan-diabetic rats have demonstrated the detrimental effects on reproduction brought about by a deficiency of insulin .
Irregular
and prolonged estrous cycles are often characteristic of diabetic rats (1,2) . Complete cess.atian of estrous cycles in diabetic rats has also been reported (3,4,5) .
When young female rats were treated with alloxan the ovaries atro-
phied and were found to contain only follicles (6) .
Liu et al . (7) have re-
ported regression in ovarian weights of immature rats treated with alloxan . The adverse effects of diabetes on reproduction could be due to reduced ovarian responsiveness to gonadotropins . experiments of Farina et al .
This mechanism is suggested by the
(8) and Liu et al .
(7) .
These reports however
disagree with the earlier findings of Shipley and parley (3) .
Diabetes may
also impair gonadotropin secretion as suggested by the experiments with parabiotic rats reported by Shipley (6) .
In experiments with male rats reduced 289
290
Alloxan Diabetes end Gonadotropin Secretion
Vol . 14, No, 2
serum levels of both follicle stimulating hormone (FSH) and luteinizing hormoms (~) have been demonstrated 8 days following alloxan treatment (9) .
In
mature females however, no reduction in serum levels of either gonadotropin was found 7 days after alloxan treatment (7) . In the following experiments, the effect of alloxan treatment on ovarian weights and on pituitary and serum levels of FSH and IH in female rats of two ages was determined . MATERIALS AND METHODS Tlvo experiments were conducted using female Sprague-Dawley rats from our own colony .
In the first experiment the rats were 35 days old while in the
second experiment the rats were 95 days old when the treatment was initiated . The animals were maintained in individual cages in a light (12 hr light, 12 hr dark) and temperature (74 ± 1 °F) controlled room and received Purina Lab Q~ow and distilled water ad libitum .
In each experiment the animals were ass-
igned to treatment groups, allowed several days to become accustomed to the individual cages and then fasted for 24 hours .
At the end of the fasting per-
iod the treated animals were injected intraperitoneally with alloxan monohydrate dissolved in 0 .9$ saline at doses of 15 mg/100 g body weight (high dose) or 7 .5 m8/100 g body weight (low dose) .
The low dose of alloxan was included
to determine if a sub-diabetogenic dose of the drug would affect any of the characteristics studied .
Urine glucose levels were determined daily using
Tes Tape (Eli Lilly F, Co .) .
Rats receiving the high dose of alloxan showed
urine glucose levels of at least 2 percent throughout the 21-day experimental period .
Although most of the rats receiving the low dose of elloxan initially
showed measurable glucose in the urine, by day 21, with the exception of one or two animals in each experiment, the urine glucose tests were negative and the animals showed no other evidence of diabetes . In the horning an day 21 and following a 16-hr fast, the rats were anesthetized with ether and blood samples were obtained by heart puncture . animals were then killed and anterior pituitaries and ovaries were removed
The
Vol. 14, No . 2 and weighed .
Alloxan Diabetes and Gonedotropin Secretion
291
Sera and pituitary glands were frozen until assayed for glucose
and gonadotropins .
Serum glucose levels were determined by a glucose oxidase
method (Glucostat, Worthington Biochemical Corp .) .
The concentration of LH
in pituitary homogenates and sera was determined using the ovine-ovine radioimmunoassay described by Niswender et al . (10) . rat-LH-RP-1 .
The standard used was NIAMD
A similar double antibody radioismtmoassay distributed by the
National Institute of Arthritis and Metabolic Diseases, NIH, was used to measure FSH concentration .
Data for FSH were expressed in terse of NIAMD rat-FSH-
RP-1 . The significance of differences between treatment groups were determined by Duncan's Multiple Range Test (11) . RESULTS The effects of alloxan-treatment in 35-day old rats are shown in Table 1 . the low dose of alloxan did not affect any of the characteristics studied with the exception of serum glucose concentration .
Serum glucose was slightly,
but significantly elevated in the low dose rats as compared to controls .
The
rats receiving the high dose of alloxan had significantly lower body weight gains during the experimental period than did the control rats .
Rats on the
high dose also had significantly lower pituitary and ovarian weights than did either control rats or those receiving the low dose of alloxan.
The serud
glucose level was significantly elevated in rats on the high dose when compared with either of the other groups .
Although no differences were detected
in pituitary concentration of W, the serum level of this hormone in rats receiving the high dose was reduced to approximately half that observed in control rats or rats receiving the low dose of alloxan .
In contrast to LH, the
pituitary concentration of FSH was elevated in rats receiving the high dose of alloxan, but the serum levels of this hormone did not differ significantly between groups . the results of the second expérinent in which older animals were studied are s++~+~+ zed in Table 2 .
As noted in the younger animals, the low dose
Vol : 14, No . 2
Alloxan Diabetes and Gonadotmpin Secretion
292
TABIE 1 Effect of Alloxan Treatment on Body Weight Gain, Organ Weights, Serum Glucose Concentration and Gonadotropin Levels in Young * Female Rats . Alloxan treatment High dose Characteristic Control Low dose + Number of rats
6
7
9
228 227 t 6 t ± 6 Body weight (g) Body weight gain (g)
74 ± 3a
181 ± 10
68 ± 5a'b
Serum lucose conc . (mg/lÔ0 ml)
75 .7 ± 2 .2 a
Ovarian weight (mg)
85 ± 2a
88 ± 7a
8 .9 ± 0 .9a
9 .3 ± 0 .6a
Pituitary weight (mg)
49 ± lOb
b
90 .6 t 2 .8
324 .8 ± 31 .2 59 + 7b 6 .4 ± 0 .5b
Pituitary Lfi conc . (ug/mg)
1g .5 t 1 .5
18 .7 t 2 .1
20 .1 ± 1 .9
Pituitary FSH conc . (ug/mg)
2 .60 ± 0 .22a
2 .41 ± 0 .17a
4 .11 ± 0 .48b
Serum LH conc . (ng/ml)
62 .5 ± 8 .2a
63 .6 ± 11 .7a
32 .5 t 4 .2 b
Serum FSH conc . (ng/ml)
231 t 24
232 ± 22
c
245 t 18
35 days old at time of alloxan injection . + Low dose = 7 .5 mg/100 g body weight, high dose weight .
15 mg/100 g body
tMean t S .E . a ' b ' cMeans with different superscripts are significantly different (P<0 .05) .
of alloxan was ineffective in altering the characteristics studied .
the rats
receiving the high dose of allozan had significantly reduced body weight gains and elevated saran glucose levels,
the reduced ovarian and pituitary weight
noted in the younger diabetic rats did not occur in the old diabetic rats . addition, treatment effects on neither pituitary nor serum levels of FSH or
In
293
Alloxen Diabetes and Gonadotropin Secretion
Vol . 14, No . 2
TABLE 2 Effect of Alloxan Treatment on Body IYeigktt Gain, Organ Weights, Serum Glucose Concentration and Gonadotropin Levels in Old' Fessle Rats . Alloxan trcatment Characteristic
Control
Number of rats
12
Body weight (g) Body weight gain (g)
280 ± 6t
Low dose +
High dose
9
11
289 t 8
258 ± 10
25 t 3 $
23 t 5 a
-3 t 6b
Serum glucose conc . (mg/100 ml)
118 t 5 a
151 t 36 a
400 t 51b
Ovarian weight (mg)
78 ± 3
87 1 5
ß2 t 6
Pituitary weight (Ag)
14 .6 f 0 .5
14 .2 t 0 .9
13 .1 ± 0 .7
Pituitary LH conc . (ug/mg)
10 .1 ± 1 .2
12 .9 t 1 .7
10 .2 t 1 .6
Pituitary FSH cons . (Vg/=g)
1 .54 ± 0 .06
1 .59 t 0 .10
1 .70 t 0 .20
Serum LH conc . (ng/ml)
32 .7 t 2 .0
36 .6 t 2 .5
Serum FSH conc . (ng/ml)
255 3 23
244 ± 30
t
~
30 .2 ± 3 .2 285 t 28
95 days old at time of alloxan injection
+ Low dose = 7 .5 mg/100 g body weight ; high dosa ~ 15 mg/100 g body weight . ' t ldean ± S .E . a,b~~s
with different superscripts are significantly different (P<0 .05) .
W ware found . DISCUSSION the results of the present experinants demonstrate that in spite of the numerous toxic effects of the drug (12}, a sub-diabetogenic dose of alloxan produced no lasting effects on gonadotropin secsetion in the feaale rat .
It
Alloxaa Diabetes and Gonadotropin Secretion
294
Vol . 14, No. 2
is possible that pituitary and seras levels of gonadotropins had been affected following injection of the drug but that recovery had occurred by the end of the 21-day period .
Previous work with male rats using a higher dose (15
mB/100 g body weight) indicated that pituitary and serum levels of both gonadotropins were depressed at 8 days after injection of alloxan (9) . The animals receiving the high dose of alloxan in each of the experiments were considered to be diabetic as indicated by urine and serum glucose levels as well as body weight changes .
It was presumed that these animals
were not showing morsel estrous cycles, although we have no data to confirm that assusption,
there are numerous reports of prolonged estrous cycles or
complete absence of estrous cycles in diabetic rats (1,2,3,4,5) .
In the pre-
sent study the young diabetic rats showed reduced ovarian weights as has been reported by others (5,6,7) . not alter ovarian weight .
In the old rats, however, alloxan treatment did the gross appearance of some of the ovaries from
diabetic rats of both ages differed fros normal ovaries due to the presence of large, pale corpora tutee .
This observation suggests that diabetes result-
ed in prolonged maintenance of corpora lutes and therefore ovarian weight was probably not a good measure of ovarian activity in diabetics of either age . Lawrence and Contopoulos (5) reported persistent corpora lutes in rats treated with alloxan at 40 days of age and autopsied 62 days later .
17îe ovaries
in their diabetic rats were below normal in size . 11îe pituitary and serum gonadotropin assays provide evidence that gonadotropin secretion had been affected by diabetes in the young rats .
The
reduced basal levels of LH could have been responsible for the reduction in ovarian weight .
Since there was no increased storage of hormone in the pit-
uitary gland it must be assumed that both synthesis and release of hormone had been reduced . betic rats .
The pituitary levels of FSH were elevated in the young dia-
This effect is difficult to interpret since serum levels of FSH
were not affected by treatment .
The mechanism whereby alloxan induced dia-
betes codifies pituitary gonadotropin synthesis and release remains to be
Vol . 14, No. 2 investigated .
295
Allo :aa Diabetes and C,ooadotcopin Secretion
It is of interest to note that the treatsent effects on gona-
dotropins in young rats i .e ., reduced serim LH levels without changes in pituitary LH and elevated pituitary FSH levels without changes in soma FSH, have been reported in fes+sle rats that were underfed (13) .
These effects app-
ear to be aore . eaaily produced by underfeeding than by rendering animals diabetic and even occur in old rats (13) .
This is probably explained by the
fact that underfeeding is a more severe metabolic stress than diabetes as indicated by body weight changes .
Underfed rats show considerable weight loss-
es (13) while the diabetic rats in this study either asintained their starting body weight or actually showed a slaved rate of growth .
Although the cal-
oric intake is greater than normal in diabetic rats (14) and less than noroel in underfed rats, the effects at the cellular level in the hypothalamus and/ or pituitary gland, as reflected by changes in ganadotropin levels, appear to be similar . ACIWOIiIBD(;BNEriTS The authors are grateful to Dr . G .D . Niswender, Dr . L .E . Reichert, Jr ., and the National Institute of Arthritis and Metabolic Diseases, Rat Pituitary Hormone Prograa for providing the materials used in the radioiasamoassays . This study was supported by grants MA-4454 and !dA-3627 from the Dbdical Research Council of Canada . REFERENCES 1.
M .E . RAVIS, N .K . FUGO and X . G . 1 .AlIRENCE, Proc . Soc . Exp . Biol . Med . 66, 638-641 (1947) .
2.
J .E . LEVI and T . IIEINBERG, Proc . Soc . Exp . Biol . lied . 72, 658-662 (1949) .
3.
E .G . SHIPLEY and K .S . DANLEY, Aver . J . Physiol . 150, 84-94 (1947) .
4.
J .A . SINDEN and B .B . LONGt1ELL, Proc . Soc . Exp . Biol . Med . (1949) .
5.
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