The influence of aging on androgen dynamics in the male rat

Abstract

Androgen assimilation was investigated in a variety of accessory sex organs (seminal vesicles and anterior, dorsal, lateral, and ventral prostates) and in several nonaccessory sex organs in male Wistar rats. After administration of a pulse dose of [ 3H]testosterone in vivo to intact young (3–4 months old) rats, [ 3H]testosterone was the primary radioactive steroid recovered from most organs examined, except for the secondary sex glands where the reduced metabolites, [ 3H]5α-dihydrotestosterone (DHT) and [ 3H]5α-androstanediol(s), predominated. At longer postinjection times, [ 3H]DHT was preferentially retained in the accessory sex glands, presumably reflecting intracellular metabolism of [ 3H]testosterone to this compound and subsequent specific binding of [ 3H]DHT to receptor proteins. At the longest postinjection interval investigated, the ventral prostate retained greater concentrations of [ 3H]DHT than the lateral prostate which in turn had a higher [ 3H]DHT concentration than the seminal vesicles or anterior or dorsal prostates. The latter three glands retained approximately equal concentrations of [ 3H]DHT. Scatchard plot analyses of cytosol binding in 24-h castrates indicated that with one exception, the level of high affinity DHT binding sites was generally correlated with the retention of [ 3H]DHT in vivo in intact rats. Specifically, while the affinity for DHT binding in all accessory sex organs was the same, the number of high affinity binding sites per mg wet tissue weight was on the order of ventral prostate > anterior prostate ≥ seminal vesicles ≥ dorsal prostate > lateral prostate. Studies of the influence of aging to 22–26 months revealed no apparent differences in the affinity of the DHT receptor for its ligand in any of the accessory sex glands from 24-h castrates when the receptors were present in levels sufficiently high to quantify. The concentration of available DHT receptors with advancing age remained constant in the anterior and dorsal prostates, increased in the seminal vesicles, and declined in the ventral and lateral prostates. The decreases observed in the ventral prostate were only partial, but the receptors of the lateral prostate declined to nondetectable levels.