Acquisition of Regulatory Mechanisms for Gonadotropin Receptors and Steroidogenesis in the Maturing Rat Testis

TLDR: Testicular LH, lactogen, and estrogen receptors and in vitro steroidogenic and cAMP responses were measured in rats between the ages of 1 and 60 days, and there was no direct correlation between the concentrations of the two receptors.

Abstract: Testicular LH, lactogen, and estrogen receptors and in vitro steroidogenic and cAMP responses were measured in rats between the ages of 1 and 60 days. Testicular LH and lactogen receptors increased gradually with advancing age, although there was no direct correlation between the concentrations of the two receptors. Cytosolic estrogen receptors were present in the testis at 6 days of age, but α-fetoprotein represented the major estrogen-binding component until 20 days of age. The basal and maximally stimulated in vitro production rates of testosterone, pregnenolone, and cAMP per unit weight were more than 10-fold higher in neonatal rats than in 60-dayold animals. These production rates decreased rapidly to a nadir at 15 days and increased again between 15 and 60 days of age. Treatment of 1-day-old rats with a low dose of hCG (10 IU/kg daily) for 3 days caused an increase of 91% (P < 0.01) -in LH receptors per testis. This effect of hCG diminished gradually with advancing age and became insignificant in an...