Evidence for changes in sensitivity to testosterone negative feedback on gonadotropin release during sexual development in the male rat

A. Negro Vilar, Sergio Ojeda, S. M. McCann

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Male rats were castrated at different ages and injected sc once daily for 2 days with either oil or various doses of testosterone propionate (TP). Castration elevated serum gonadotropins at all ages was studied from day 15 to day 88, but the response was maximal for LH at 58 days and minimal at 15 days. The elevation of FSH was minimal at 88 days but similar at other ages. Whereas 10 μg/100 g body wt of TP were sufficient to prevent the rise in serum FSH and LH which occurred 2 days after castration in 15 day old rats and 10 μg were still effective in 28 day old animals, the suppressibility of serum gonadotropins decreased with age and by 58 days the 10 μg/100 g body wt dose was no longer effective. Higher doses of TP suppressed the increase in serum LH and FSH at all ages studied. The results suggest that the sensitivity of the hypothalamic pituitary unit to the negative feedback of testosterone declines during sexual development and that this change, which is especially noticeable at the time of puberty, may be responsible for maintenance of gonadotropin release in the face of rising testosterone levels and play a role in the induction of puberty. In another experiment, the initiation of TP replacement therapy was delayed for 5 days. In contrast to the results when replacement was initiated immediately, differential sensitivity of LH to TP at 20 and 60 days of age could not be demonstrated under these conditions. In this situation, the 25 μg dose was able to prevent partially the post castration rise in FSH at 60 days, whereas both 10 and 25 μg doses were ineffective at 20 days. These findings suggest that removal of the gonads in the immature male rat elevates the setpoint of the feedback system, setting it at the higher level of androgens encountered in the mature animal.

Original languageEnglish (US)
Pages (from-to)729-735
Number of pages7
JournalEndocrinology
Volume93
Issue number3
StatePublished - 1973
Externally publishedYes

Fingerprint

Testosterone Propionate
Sexual Development
Gonadotropins
Testosterone
Castration
Puberty
Serum
Hypothalamo-Hypophyseal System
Gonads
Androgens
Oils
Maintenance

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Evidence for changes in sensitivity to testosterone negative feedback on gonadotropin release during sexual development in the male rat. / Negro Vilar, A.; Ojeda, Sergio; McCann, S. M.

In: Endocrinology, Vol. 93, No. 3, 1973, p. 729-735.

Research output: Contribution to journalArticle

@article{3dce6f2624df435bb9ed1f36719ed4ea,
title = "Evidence for changes in sensitivity to testosterone negative feedback on gonadotropin release during sexual development in the male rat",
abstract = "Male rats were castrated at different ages and injected sc once daily for 2 days with either oil or various doses of testosterone propionate (TP). Castration elevated serum gonadotropins at all ages was studied from day 15 to day 88, but the response was maximal for LH at 58 days and minimal at 15 days. The elevation of FSH was minimal at 88 days but similar at other ages. Whereas 10 μg/100 g body wt of TP were sufficient to prevent the rise in serum FSH and LH which occurred 2 days after castration in 15 day old rats and 10 μg were still effective in 28 day old animals, the suppressibility of serum gonadotropins decreased with age and by 58 days the 10 μg/100 g body wt dose was no longer effective. Higher doses of TP suppressed the increase in serum LH and FSH at all ages studied. The results suggest that the sensitivity of the hypothalamic pituitary unit to the negative feedback of testosterone declines during sexual development and that this change, which is especially noticeable at the time of puberty, may be responsible for maintenance of gonadotropin release in the face of rising testosterone levels and play a role in the induction of puberty. In another experiment, the initiation of TP replacement therapy was delayed for 5 days. In contrast to the results when replacement was initiated immediately, differential sensitivity of LH to TP at 20 and 60 days of age could not be demonstrated under these conditions. In this situation, the 25 μg dose was able to prevent partially the post castration rise in FSH at 60 days, whereas both 10 and 25 μg doses were ineffective at 20 days. These findings suggest that removal of the gonads in the immature male rat elevates the setpoint of the feedback system, setting it at the higher level of androgens encountered in the mature animal.",
author = "{Negro Vilar}, A. and Sergio Ojeda and McCann, {S. M.}",
year = "1973",
language = "English (US)",
volume = "93",
pages = "729--735",
journal = "Endocrinology",
issn = "0013-7227",
publisher = "The Endocrine Society",
number = "3",

}

TY - JOUR

T1 - Evidence for changes in sensitivity to testosterone negative feedback on gonadotropin release during sexual development in the male rat

AU - Negro Vilar, A.

AU - Ojeda, Sergio

AU - McCann, S. M.

PY - 1973

Y1 - 1973

N2 - Male rats were castrated at different ages and injected sc once daily for 2 days with either oil or various doses of testosterone propionate (TP). Castration elevated serum gonadotropins at all ages was studied from day 15 to day 88, but the response was maximal for LH at 58 days and minimal at 15 days. The elevation of FSH was minimal at 88 days but similar at other ages. Whereas 10 μg/100 g body wt of TP were sufficient to prevent the rise in serum FSH and LH which occurred 2 days after castration in 15 day old rats and 10 μg were still effective in 28 day old animals, the suppressibility of serum gonadotropins decreased with age and by 58 days the 10 μg/100 g body wt dose was no longer effective. Higher doses of TP suppressed the increase in serum LH and FSH at all ages studied. The results suggest that the sensitivity of the hypothalamic pituitary unit to the negative feedback of testosterone declines during sexual development and that this change, which is especially noticeable at the time of puberty, may be responsible for maintenance of gonadotropin release in the face of rising testosterone levels and play a role in the induction of puberty. In another experiment, the initiation of TP replacement therapy was delayed for 5 days. In contrast to the results when replacement was initiated immediately, differential sensitivity of LH to TP at 20 and 60 days of age could not be demonstrated under these conditions. In this situation, the 25 μg dose was able to prevent partially the post castration rise in FSH at 60 days, whereas both 10 and 25 μg doses were ineffective at 20 days. These findings suggest that removal of the gonads in the immature male rat elevates the setpoint of the feedback system, setting it at the higher level of androgens encountered in the mature animal.

AB - Male rats were castrated at different ages and injected sc once daily for 2 days with either oil or various doses of testosterone propionate (TP). Castration elevated serum gonadotropins at all ages was studied from day 15 to day 88, but the response was maximal for LH at 58 days and minimal at 15 days. The elevation of FSH was minimal at 88 days but similar at other ages. Whereas 10 μg/100 g body wt of TP were sufficient to prevent the rise in serum FSH and LH which occurred 2 days after castration in 15 day old rats and 10 μg were still effective in 28 day old animals, the suppressibility of serum gonadotropins decreased with age and by 58 days the 10 μg/100 g body wt dose was no longer effective. Higher doses of TP suppressed the increase in serum LH and FSH at all ages studied. The results suggest that the sensitivity of the hypothalamic pituitary unit to the negative feedback of testosterone declines during sexual development and that this change, which is especially noticeable at the time of puberty, may be responsible for maintenance of gonadotropin release in the face of rising testosterone levels and play a role in the induction of puberty. In another experiment, the initiation of TP replacement therapy was delayed for 5 days. In contrast to the results when replacement was initiated immediately, differential sensitivity of LH to TP at 20 and 60 days of age could not be demonstrated under these conditions. In this situation, the 25 μg dose was able to prevent partially the post castration rise in FSH at 60 days, whereas both 10 and 25 μg doses were ineffective at 20 days. These findings suggest that removal of the gonads in the immature male rat elevates the setpoint of the feedback system, setting it at the higher level of androgens encountered in the mature animal.

UR - http://www.scopus.com/inward/record.url?scp=0015753439&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0015753439&partnerID=8YFLogxK

M3 - Article

C2 - 4721297

AN - SCOPUS:0015753439

VL - 93

SP - 729

EP - 735

JO - Endocrinology

JF - Endocrinology

SN - 0013-7227

IS - 3

ER -