The effect of age on the activity of cholesterol side-chain cleavage in rat testis.

Abstract

The enzymatic activity of side-chain cleavage of cholesterol and 20α-hydroxycholesterol in rat testes aged 3 week to 20 month old was determined. The activity of cholesterol side-chain cleavage was low in testes of the 3 week old rats. The activity then increased rapidly as animals matured and reached the highest level at 4 months. Thereafter, the activity remained constant throughout the experimental period. Changes in the activity of 20α-hydroxycholesterol side-chain cleavage exhibited nearly the identical pattern as that of cholesterol side-chain cleavage.Cleavage of the cholesterol side-chain to yield pregnenolone seems to be an important step in the biosynthesis of androgens by testicular tissue, since it has been reported that gonadotrophic hormones regulate this step. The histological examination of the 20 month old testes revealed very little spermatogenesis in these tissues. Nevertheless the activity of cholesterol side-chain cleavage remained at the level of the 4 month old rats. These results suggest that the availability of pregnenolone for androgen biosynthesis is almost et al. constant between young matured rats and aged ones. Axelrod and Snipes have reported a decline in activities of C-17, 20-desmolase and 17β-hydroxysteroid dehydrogenase in testes of aged subjects. Thus, it may be possible that the regulation of steroid hormone biosynthesis in testes of aged animals is controlled by mechanisms other than the side-chain cleavage of cholesterol.