Biphasic effect of exogenous testosterone on follicle-stimulating hormone gene expression and synthesis in the male rat.
Effects of 2-week treatments with increasing doses of testosterone (T) on gonadotropin gene expression and secretion were studied in intact and acutely castrated male rats. T was administered in silastic capsules with lengths of 2, 4, 8 or 16 cm, and control animals received empty capsules (eight per treatment). The treatments increased serum T up to 3-fold of control levels. In intact animals, the 2-8 cm capsules suppressed pituitary follicle-stimulating hormone-beta (FSH beta) mRNA contents by 40-50% (p < 0.01), but 16 cm of T returned the levels back to control range. Castration alone increased the FSH beta mRNA level 2.3-fold (p < 0.01) and, after T treatment, the FSH beta message returned to control levels indistinguishable from intact controls but higher than in intact animals receiving the same T dose. Pituitary luteinizing hormone-beta (LH beta) mRNA displayed a dose-dependent suppression in response to T, to 32-35% of controls (p < 0.01) with the 8 and 16 cm capsules. Castration increased this message 10-fold, and additional T treatment suppressed the levels to the range of T-treated intact animals. Pituitary common-alpha mRNA decreased to 30-31% of controls by 2, 4 and 8 cm of T (p < 0.01), but the highest dose of T increased the common-alpha contents, in comparison to the other doses, to 54% of controls (p < 0.01). Castration alone increased the common-alpha contents 4.4-fold, and there was a dose-dependent suppression of this parameter by T down to the range of T-treated intact rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Perheentupa
A
A
Department of Physiology, University of Turku, Finland.
de Jong
F
F
Huhtaniemi
I
I
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D005246:Feedback; D005640:Follicle Stimulating Hormone / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007265:Inhibins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D007986:Luteinizing Hormone / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008297:Male; D009919:Orchiectomy; D009929:Organ Size / Q000187:drug effects; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011467:Prostate / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012669:Seminal Vesicles / Q000473:pathology; D013737:Testis / Q000473:pathology; D013739:Testosterone / Q000494:pharmacology*
D004343:Drug Implants; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone