Testosterone metabolism by the prostate of the aging canine

Examination of testosterone metabolism in the dorsal, lateral, and ventral regions of the beagle prostate showed an absence of regional heterogeneity for testosterone metabolite production and metabolic capacity. Testosterone metabolism by the hyperplastic prostate of aged beagles (11.1 years old) was distinguished from that of young mature (2.5-year-old) and mature adult (4.5-year-old) beagle prostate by increased reductive metabolism. The change was principally the consequence of increased production of 5 alpha-dihydrotestosterone and decreased production of 4-androstenedione. These alterations in testosterone metabolism occurred progressively and may be weakly linked to other changes in canine prostate which occur during aging. 5 alpha-Androstane-3 alpha, 17 beta-diol production was maximal for prostate from 4.5-year-old beagles and the amount of this metabolite produced appeared to be unrelated to prostate size. Co-incubation of prostate from any of the beagles with testosterone and estradiol showed that estradiol had no in vitro effect upon testosterone metabolism. Mean plasma testosterone content of aged beagles (11.1 years old) was not significantly different from that of younger individuals; however, the heterogeneity of the values for the subject groups was notable. The data demonstrate that the consequences of aging upon testosterone metabolism by canine prostate, which principally develops benign prostatic hyperplasia, are opposite to those characteristic of senescent rat prostate, which does not develop bening prostatic hyperplasia and has a high incidence of spontaneous adenocarcinoma.