CIRCADIAN FLUCTUATIONS OF SERUM HORMONE LEVELS IN PREPUBERTAL MALE AND FEMALE RATS

1976 ◽  
Vol 83 (2) ◽  
pp. 269-279 ◽  
Author(s):  
K. D. Döhler ◽  
W. Wuttke
Keyword(s):  
Age Groups ◽  
Serum Testosterone ◽  
Female Rats ◽  
Serum Prolactin ◽  
Male And Female ◽  
Hormone Levels ◽  
Male And Female Rats ◽  
Serum Lh ◽  
Serum Hormone ◽  
Old Females

ABSTRACT Diurnal variations in serum hormone levels during 2 different stages of prepubertal development were investigated in male and female rats. Groups of 13 to 18 and 25 to 30 day old male and female rats were decapitated at 4-hour by intervals during a period of 24 h. Their blood was collected and hormones were measured by radio-immunoassay. FSH levels were constantly high in 13 to 18, but low in 25 to 30 day old females. FSH was low in younger males, and significantly higher but without diurnal fluctuations in the older males. Serum LH was low in approximately 40% of the 13 to 18 day old females, while 40% had moderately high levels, and the remaining females extremely high levels of the hormone. Most of the extremely high LH peaks were found at 15.00 h and some at 03.00 h. Older females and males of both age groups had constantly low serum LH levels. Serum oestradiol was high in males and females during days 13 to 18, but it was lower in the 25 to 30 day old animals. In the young females prolactin was slightly elevated between 15.00 h and 19.00 h, while in the males the serum prolactin fluctuations were not significant. Serum testosterone was low in females at all times. The 13 to 18 day old males had higher testosterone levels than the 25 to 30 day old males. Both groups showed slight, but insignificant fluctuations in serum testosterone. These results confirm result published previously and furthermore they demonstrate the existence of circasemedian or circadian rhythms for both the gonadotrophins and gonadal steroids. These results, also suggest that the maturation of the positive feedback action of oestradiol on gonadotrophin release in female rats occurs between day 10 and 20.

EFFECT OF SYNTHETIC THYROTROPHIN RELEASING FACTOR ON PROLACTIN AND LUTEINIZING HORMONE SECRETION IN MALE AND FEMALE RATS DURING VARIOUS REPRODUCTIVE STATES

1975 ◽  
Vol 67 (3) ◽  
pp. 425-430 ◽  
Author(s):  
R. P. DEIS ◽  
NIA ALONSO
Keyword(s):  
Hormone Secretion ◽  
Female Rats ◽  
Male Rats ◽  
Serum Prolactin ◽  
Serum Prolactin Level ◽  
Luteinizing Hormone Secretion ◽  
Male And Female Rats ◽  
Serum Lh ◽  
The Mean ◽  
Lh Secretion

SUMMARY The effect of synthetic thyrotrophin releasing factor (TRF) on serum prolactin and LH concentrations was determined by radioimmunoassay in male, cyclic and pseudopregnant female rats. A solution of TRF (0·1, 0·25, 0·5 and 1 μg/rat) was injected i.v. at 17.00 h into rats pretreated with sodium pentobarbitone at 13.00 h. A group of male rats was also treated with TRF at 11.00 h after pretreatment with sodium pentobarbitone at 07.00 h. Fifteen minutes after TRF administration, blood samples were obtained by heart puncture. Doses of 0·25, 0·5 and 1 μg TRF significantly increased the serum prolactin concentration in pro-oestrous rats. The mean serum prolactin level after the injection of 0·5 and 1 μg into oestrous rats and 0·5 μg TRF into dioestrous day 2 rats, was significantly greater than the control values. Injection of TRF on day 1 of dioestrus had no effect. Serum LH concentration was not significantly modified by the various doses of TRF administered. On day 3 of pseudopregnancy a significant increase of serum prolactin values was obtained with 0·5 and 1 μg TRF. On day 7 of pseudopregnancy a dose of 0·5 μg produced the same effect, but on day 10 of pseudopregnancy only 1 μg TRF significantly increased serum prolactin levels when compared with the control rats. In male rats serum prolactin concentration was significantly greater than the control values after TRF treatment either in the morning or the afternoon. The response was similar to that obtained in pro-oestrous rats. The results suggest that the ability of synthetic TRF to stimulate prolactin release exists in both female and male rats and that TRF does not affect LH secretion.

THE EFFECTS OF AN ALPHA ADRENERGIC BLOCKER ON THYROCALCITONIN ACTIVITY IN MALE AND FEMALE RATS

1973 ◽  
Vol 73 (1) ◽  
pp. 64-68
Author(s):  
G. N. Currie ◽  
D. L. Black
Keyword(s):  
Serum Calcium ◽  
Age Groups ◽  
Blocking Agent ◽  
Female Rats ◽  
Male Rats ◽  
Male And Female ◽  
Male And Female Rats ◽  
Adrenergic Blocker ◽  
Effective Level ◽  
Adrenergic Blocking

ABSTRACT When an alpha adrenergic blocking agent, phenoxybenzamine, was given to rats prior to the administration of a non-effective level of thyrocalcitonin (TC) there resulted a significant fall in serum calcium one hour following TC treatment. This response was observed in two different age groups of female rats but did not occur in male rats.

Effects of corticotropin-releasing factor on energy balance in rats are sex dependent

1989 ◽  
Vol 257 (6) ◽  
pp. R1417-R1422 ◽  
Author(s):  
S. Rivest ◽  
Y. Deshaies ◽  
D. Richard
Keyword(s):  
Body Weight ◽  
Energy Balance ◽  
Food Intake ◽  
Serum Testosterone ◽  
Corticotropin Releasing Factor ◽  
Female Rats ◽  
Male Rats ◽  
Male And Female ◽  
Male And Female Rats ◽  
Significant Difference

The purpose of this study was to investigate the effects of a chronic intracerebroventricular administration of corticotropin-releasing factor (CRF) on energy balance of male and female rats. One week after their delivery to the laboratory, both male and female rats were divided into two groups. One group in each sex was treated with human/rat CRF, while another group was infused with the vehicle. Chronic administration of CRF was accomplished by means of miniosmotic pumps connected to a cannula that was stereotaxically directed into the third ventricle. Food intake and body weight were measured each day during the study. After 14 days of treatment, the rats were killed by decapitation. Energy, fat, and protein contents of the carcasses were quantified. Serum testosterone and estradiol were assayed in males and females, respectively. Administration of CRF significantly reduced body weight gain and food intake in male rats. No significant difference in those variables was observed between female rats treated with CRF and their controls infused with saline. Similarly, metabolizable energy intake and body energy gain were reduced in male rats infused with CRF, whereas no difference was observed between female animals treated with CRF and those infused with saline. In male rats, body fat and body protein contents were lower in CRF-treated than in saline-infused rats. In female rats, CRF did not affect body composition. Serum testosterone in male rats and serum estradiol in female animals were reduced after chronic infusion of CRF.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal age, reproduction and chromosomal aberrations in Wistar derived rats

1994 ◽  
Vol 28 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Adolf Niggeschulze ◽  
Alexander Kast
Keyword(s):  
Risk Assessment ◽  
Bone Marrow ◽  
Maternal Age ◽  
Age Groups ◽  
Female Rats ◽  
Age Group ◽  
Male And Female ◽  
Male And Female Rats ◽  
Copulation Rate ◽  
New Compounds

The fertility of rats ranges from one to 18 months. In standard teratogenicity testing young, mature females are used which may not reflect the situation in women above 35 years old. Reproduction among different age groups of Wistar ats (strain Chbb : THOM) was compared at 3, 6, 9, 12, 15 and 18 months. At least 20 virgin females were inseminated per age group. The copulation rate did not differ between the groups. From the maternal age of 12 months, the pregnancy rate was significantly decreased, from the age of 9 months, the litter values were significantly lowered and the resorption rates were increased. Maternal age did not influence the incidence of fetal variations and malformations. Additionally, the chromosomal aberration rate in the bone marrow was evaluated in male and female rats. Twelve animals of each sex were scheduled per group, and studied at the age of 1, 3, 6, 12, 15, 18, 21 or 24 months. In males, the aberration rate increased continuously from 0.18 through 3%, while in females the increase continued from 0.33 to 2.29% at 15 months old when a plateau was reached. When testing new compounds for embryotoxicity or genotoxicity in female rats, the animals should be of comparable age to man in order to avoid a misinterpretation of spontaneous abnormalities. From these studies, however, it was concluded that the use of higher age groups of female rats in teratogenicity studies would not improve the risk assessment.

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