Biology of Reproduction, Vol 52, 808-813, Copyright © 1995 by Society for the Study of Reproduction

ARTICLES

Modulation of gonadotropin secretion at the pituitary level by testosterone in gonadotropin-releasing hormone-treated male rats during food deprivation

A Perheentupa, M Bergendahl and I Huhtaniemi
Department of Physiology, University of Turku, Finland.

Testosterone (T) inhibits the synthesis and secretion of FSH and LH by decreasing the secretion of GnRH from the hypothalamus. However, T is also able to stimulate FSH gene expression and synthesis at the pituitary level when the release or action of GnRH is blocked. In the present study, we analyzed whether the positive effect of T on pituitary FSH could also be brought about during food restriction, which represents a model of suppressed GnRH secretion. We also wanted to learn whether this positive effect could be detected if GnRH pulsatility is maintained by exogenous injections. Adult male rats were subjected to various combinations of the following treatments: 1) implantation of silastic capsules containing T for Days 0-4 of the experiment, 2) starvation for Days 1-4 of the experiment, and 3) GnRH- treatment at 2-h intervals (500 ng/kg BW) for Days 3-4. The combined treatments were as follows: 1) control, 2) only starvation, 3) only GnRH, 4) starvation+GnRH, 5) only T, 6) starvation+T, 7) GnRH+T, and 8) starvation+GnRH+T (n = 12/group; two independent experiments). Serum FSH level was decreased 20% by starvation (p < 0.01), but no decrease was observed when the starving animals were treated with T. GnRH treatment increased serum FSH in both ad libitum-fed and starving animals to 266% and 333% of the respective control values (both p < 0.01). When T was added to these treatments, the increases in serum FSH were smaller, 219% and 272%, respectively (p < 0.01 vs. respective groups without T).(ABSTRACT TRUNCATED AT 250 WORDS)