Testosterone regulates progonadotropin-releasing hormone levels in the preoptic area and basal hypothalamus of the male rat.
GnRH is synthesized as part of a larger 92-amino acid prohormone (pro-GnRH). In the present study, we examined the effect of gonadectomy and hormone replacement on the processing of pro-GnRH to GnRH in adult male rats. Immunoreactive levels of pro-GnRH and GnRH in acid extracts of preoptic area (POA) and basal hypothalamus (BH) from intact, castrate, and testosterone (T)-treated castrate males were quantified by RIA. In addition, we used immunocytochemistry to detect pro-GnRH-and GnRH-positive neurons and determine the effects of hormone treatment. Three weeks after castration, the pro-GnRH content of the POA was 2-fold greater than the amount found in intact males. Treatment with T for 1 week lowered the prohormone content to intact levels. Although the pro-GnRH content in the BH was about 50% lower than that in the POA, the BH responded to castration and steroid replacement in a manner identical to the POA. The GnRH content of the BH, but not that of the POA, was significantly reduced after castration and increased by T treatment. On the other hand, the total number of pro-GnRH and GnRH cell bodies visualized by immunocytochemistry was not significantly altered by either treatment. These results show that changes in pro-GnRH content vary in inverse relation to changes in GnRH content and suggest that gonadectomy inhibits the enzymatic processing of precursor, while T treatment promotes it.
Roselli
C E
CE
Department of Physiology, Oregon Health Sciences University, Portland 97201.
Kelly
M J
MJ
Ronnekleiv
O K
OK
D000818:Animals; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D009919:Orchiectomy; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000494:pharmacology*
D011498:Protein Precursors; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone