Perheentupa A, de Jong F, Huhtaniemi I
Department of Physiology, University of Turku, Finland.
Mol Cell Endocrinol. 1993 Jun;93(2):135-41. doi: 10.1016/0303-7207(93)90116-2.
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)
