HYPOTHALAMIC, PITUITARY AND TESTICULAR FUNCTION DURING SEXUAL MATURATION OF THE MALE RAT

1977 ◽  
Vol 72 (1) ◽  
pp. 17-26 ◽  
Author(s):  
A. H. PAYNE ◽  
R. P. KELCH ◽  
E. P. MURONO ◽  
J. T. KERLAN
Keyword(s):  
Dehydrogenase Activity ◽  
Sexual Maturation ◽  
Hydroxysteroid Dehydrogenase ◽  
Male Rat ◽  
Releasing Hormone ◽  
Isomerase Activity ◽  
Serum Lh ◽  
Rate Of Increase ◽  
Gonadotrophin Releasing Hormone

SUMMARY Hypothalamic content of gonadotrophin-releasing hormone (GnRH), serum LH and FSH, capacity of the testis to synthesize testosterone in vitro, and testicular 5-ene-3β-hydroxysteroid dehydrogenase-isomerase and 17β-hydroxysteroid dehydrogenase were measured in groups of rats at approximately 5 day intervals from birth to day 64 and at days 74 and 89. The capacity of the testes to synthesize testosterone in vitro was measured in the presence of a saturating dose of rat LH. Gonadotrophin-releasing hormone increased steadily from 0·17 ng per hypothalamus at birth to a maximum of 7 ng at day 52 and then remained constant. LH concentrations were highly variable and often exceeded adult values between days 10 and 32. After day 32 a steady rise was observed which reached adult values between days 37 and 42. FSH concentrations markedly increased from 255 ng/ml observed at birth and day 10 to a peak value of 1000 ng/ml at day 32. Subsequently there was a steady decline in FSH values until day 74 when the concentration returned to values found at birth. 5-ene-3β-Hydroxysteroid dehydrogenase-isomerase activity exhibited a rapid increase between days 12 and 19 followed by an even greater rate of increase between days 19 and 32 when adult levels were attained. 17β-Hydroxysteroid dehydrogenase activity was very low between birth and day 22. Enzyme activity began to increase at day 22 with a rapid increase in activity observed between days 37 and 58. The increase in capacity to synthesize testosterone closely followed the increase in 17β-hydroxysteroid dehydrogenase activity. The study demonstrates that during sexual maturation in the male rat, changes in serum LH and FSH do not reflect changes in hypothalamic GnRH. The appearance of Leydig cells as monitored by 5-ene-3β-hydroxysteroid dehydrogenase-isomerase activity precedes by approximately 20 days the increase in testicular capacity to synthesize testosterone in vitro. The latter coincides with the increase in 17β-hydroxysteroid dehydrogenase activity. These results suggest that 17β-hydroxysteroid dehydrogenase is a limiting factor in the ability of the testis to respond to LH stimulation.

Suppression of pituitary-testis function in rats treated neonatally with a gonadotrophin-releasing hormone agonist and antagonist: acute and long-term effects

1989 ◽  
Vol 123 (1) ◽  
pp. 83-91 ◽  
Author(s):  
K.-L. Kolho ◽  
I. Huhtaniemi
Keyword(s):  
Body Weight ◽  
Gnrh Agonist ◽  
Gnrh Antagonist ◽  
Long Term Effects ◽  
Adult Rats ◽  
Releasing Hormone ◽  
Serum Lh ◽  
Accessory Sex Organs ◽  
Gonadotrophin Releasing Hormone

ABSTRACT The acute and long-term effects of pituitary-testis suppression with a gonadotrophin-releasing hormone (GnRH) agonist, d-Ser(But)6des-Gly10-GnRH N-ethylamide (buserelin; 0·02, 0·1, 1·0 or 10 mg/kg body weight per day s.c.) or antagonist, N-Ac-d-Nal(2)1,d-p-Cl-Phe2,d-Trp3,d-hArg(Et2)6,d-Ala10-GnRH (RS 68439; 2 mg/kg body weight per day s.c.) were studied in male rats treated on days 1–15 of life. The animals were killed on day 16 (acute effects) or as adults (130–160 days; long-term effects). Acutely, the lowest dose of the agonist decreased pituitary FSH content and testicular LH receptors, but with increasing doses pituitary and serum LH concentrations, intratesticular testosterone content and weights of testes were also suppressed (P< 0·05–0·01). No decrease was found in serum FSH or in weights of accessory sex organs even with the highest dose of the agonist, the latter finding indicating continuing secretion of androgens. The GnRH antagonist treatment suppressed pituitary LH and FSH contents and serum LH (P< 0·05–0·01) but, as with the agonist, serum FSH remained unaltered. Testicular testosterone and testis weights were decreased (P <0·01) but testicular LH receptors remained unchanged. Moreover, the seminal vesicle and ventral prostate weights were reduced, in contrast to the effects of the agonists. Pituitary LH and FSH contents had recovered in all adult rats treated neonatally with agonist and there was no effect on serum LH and testosterone concentrations or on fertility. In contrast, in adult rats treated neonatally with antagonist, weights of testis and accessory sex organs remained decreased (P <0·01–0·05) but hormone secretion from the pituitary and testis had returned to normal except that serum FSH was increased by 80% (P <0·01). Interestingly, 90% of the antagonist-treated animals were infertile. It is concluded that treatment with a GnRH agonist during the neonatal period does not have a chronic effect on pituitary-gonadal function. In contrast, GnRH antagonist treatment neonatally permanently inhibits the development of the testis and accessory sex organs and results in infertility. Interestingly, despite the decline of pituitary FSH neonatally, neither of the GnRH analogues was able to suppress serum FSH values and this differs from the concomitant changes in LH and from the effects of similar treatments in adult rats. Journal of Endocrinology (1989) 123, 83–91

Varying the patterns and concentrations of gonadotrophin-releasing hormone stimulation does not alter the ratio of LH and FSH released from perifused sheep pituitary cells

1986 ◽  
Vol 109 (2) ◽  
pp. 155-161 ◽  
Author(s):  
J. E. A. McIntosh ◽  
R. P. McIntosh
Keyword(s):  
Dose Response ◽  
Dose Interval ◽  
Follicular Phase ◽  
Pituitary Cells ◽  
Ovulatory Cycle ◽  
Short Term ◽  
Releasing Hormone ◽  
Dissociated Cells ◽  
Gonadotrophin Releasing Hormone

ABSTRACT Our aim was to determine whether release of LH and FSH can be controlled differentially by the characteristics of applied signals of stimulatory gonadotrophin-releasing hormone (GnRH) alone, free of the effects of steroid feedback or other influences from the whole animal. The outputs of both gonadotrophins were significantly correlated (r≈0·90; P<0·0005) when samples of freshly dispersed sheep pituitary cells were perifused in columns for 7 h with medium containing a range of concentrations of GnRH in various patterns of pulses. Hormone released in response to the second, third and fourth pulses from every column was analysed in detail. Dose–response relationships for both LH and FSH were very similar when cells were stimulated with 5–8500 pmol GnRH/1 in 5-min pulses every hour. When GnRH was delivered in pulses at a maximally stimulating level, the outputs of both hormones increased similarly with increasing inter-pulse intervals. Efficiency of stimulation (release of gonadotrophin/unit stimulatory GnRH) decreased (was desensitized) with increasing pulse duration in the same way for both hormones. Thus, varying the dose, interval and duration of GnRH pulses did not alter the proportions of LH and FSH released in the short-term from freshly dissociated cells. However, the same cell preparations released more LH relative to FSH when treated with maximally stimulating levels of GnRH for 3 h in the presence of 10% serum from a sheep in the follicular phase of its ovulatory cycle compared with charcoal-treated serum. Because there was no gonadotrophin synthesis under the conditions used in vitro these results suggest that changes in the LH/FSH ratio seen in whole animals are more likely to result from differential clearance from the circulation, ovarian feedback at the pituitary, differential synthesis in intact tissue or another hormone influencing FSH secretion, rather than from differences in the mechanism of acute release controlled by GnRH. J. Endocr. (1986) 109, 155–161

IN-VITRO STUDIES OF THE EFFECTS OF OESTROGEN PRETREATMENT ON THE SENSITIVITY OF THE IMMATURE FEMALE RAT PITUITARY GLAND TO STIMULATION WITH GONADOTROPHIN RELEASING HORMONE

1977 ◽  
Vol 74 (1) ◽  
pp. 11-21 ◽  
Author(s):  
M. WILKINSON ◽  
D. DE ZIEGLER ◽  
DANIELLE CASSARD ◽  
K. B. RUF
Keyword(s):  
Pituitary Gland ◽  
Brain Lesion ◽  
Culture Technique ◽  
Female Rats ◽  
Female Rat ◽  
Immature Female ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Unilateral Brain Lesion

The effects of oestrogen priming on the sensitivity of the anterior pituitary gland to stimulation with gonadotrophin releasing hormone (GnRH) was investigated in immature female rats using a new organ culture technique. Hemipituitary glands obtained from animals primed with a single dose of oestradiol benzoate (OB; 20 μg/100 g body weight) released significantly more LH when pulsed with GnRH (4 nmol/l) than did control hemipituitary glands. This potentiating effect was detectable as early as 5 days after birth. After a second stimulation, LH secretion remained high. These results were compared with those obtained from animals treated to induce increased levels of endogenous oestrogen on day 26 of life. Thus, hemipituitary glands were obtained from animals given two injections of OB, an injection of pregnant mare serum gonadotrophin (PMSG) or a unilateral brain lesion placed in the basal hypothalamus. Pituitary tissue was stimulated as before with a pulse of GnRH. Two injections of OB enhanced the sensitivity to stimulation. Conversely, both PMSG and lesion treatment severely reduced the sensitivity to GnRH, although PMSG-treated and lesioned animals have been used as models for the study of ovulation.

Effects of differential pulse frequencies of chicken gonadotrophin-releasing hormone-I (cGnRH-I) on laying hen gonadotrope responses in vitro

2009 ◽  
Vol 85 (6) ◽  
pp. 355-363 ◽  
Author(s):  
MC Soñez ◽  
CA Soñez ◽  
MT Mugnaini ◽  
M Haedo ◽  
SA Romera ◽  
...  
Keyword(s):  
Differential Pulse ◽  
Laying Hen ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone
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