Aging and Ovarian Steroidogenesis in the Rat

Abstract

Ovaries obtained from rats of 4 and 18 mo of age were incubated in vitro with ³H-pregnenolone as the added precursor. Incorporation of radioactivity into progesterone (p), 20α-dihydroprogesterone (20α-P), 17α-hydroxyprogesterone (17α-OHP), androstenedione, and testosterone were studied by serial paper and thin-layer chromatography. Significantly more P, 17α-OHP and androgen was produced by the older ovaries. Addition of hCG (100 I.U.) to the incubate increased 20α-P production in the ovaries of both age groups, depressed 17α-OHP and androgen formation in the ovaries of older rats, and had no effect on progesterone synthesis in either age group. Serum progesterone in 4-mo-old rats was 13.5 ± 1.91 ng/ml at estrus and 3.69 ± 0.9 ng/ml at diestrus, whereas serum progesterone in 18-mo-old rats was 0.85 ± 0.15 ng/ml at constant estrus and 1.23 ± 0.54 ng/ml at constant diestrus. Treatment with hCG for 20 days increased serum progesterone to 29.6 ng/ml in young rats and to 4.21 ± 2.0 ng/ml in older rats. Shorter treatments were less effective. These data reveal a definite change in steroidogenic competence in older rat ovaries.