Impaired Ventral Prostate Affinity for Testosterone in Hypophysectomized Rats

Abstract

Several studies have suggested that nongonadotrophic pituitary secretions influence growth and function of the rat ventral prostate; the basis for this hypophysial effect is unclear. In order to investigate whether hypophysectomy would alter the previously demonstrated special avidity of rat ventral prostatic tissue for testosterone from that seen in intact animals, ventral prostate uptake and discharge of radioactivity after intravenous injection of testosterone-4-14C was studied in intact, castrate and hypophysectomized adult rats. Following intravenous injection of testosterone-4-14C to normal rats, only the excretory organs, the liver, kidney and lung and the adrenal and ventral prostate yielded significantly high levels of radioactivity. Timed studies revealed rapid decrease in radioactivity in all tissues over the first 30-60 min in control rats, whereas decline in radioactivity was less in hypophysectomized animals, presumably because of impaired hepatic excretion of the isotope resulting in higher levels of radioactivity in all tissues studied. Because of varying blood levels of radioactivity between the groups studied, relative ventral prostate affinity for the labeled hormone was expressed as the ratio of ventral prostate activity to that of rectus abdominus muscle activity, a relatively nonandrogen- dependent tissue. In this manner it was shown that accumulation of radioactivity in intact and castrate rats was significantly greater than that seen in ventral prostates of hypophysectomized animals at 30 and 60 min after intravenous injection of the labeled androgen. It is suggested that the impaired localization of testosterone in the prostate of the hypophysectomized animals, shown in these studies, supports the hypothesis that certain, as yet unidentified, nongonadotrophic pituitary hormones exert their actions on prostatic growth and responsiveness to testosterone by playing a permissive role in enhancing androgen localization in the specific target organ. (Endocrinology77: 1119, 1965)