Influence of Prolactin-Producing Pituitary Grafts on the in Vivo Uptake, Distribution, and Disappearance of [3H]Testosterone and [3H]Dihydrotestosterone by the Rat Prostate Lobes*

Abstract

The effect of PRL-producing ectopic pituitary grafts on the in vivo uptake, distribution, and disappearance of testosterone and 5α-dihydrotestosterone (DHT) in the rat prostate was examined to determine if the PRL-testosterone synergism is mediated through an alteration at any of these sites. Adult rats were castrated and treated with sc Silastic implants containing testosterone (∼1.75 ng/ml serum). At the same time, two pituitaries from female rats were grafted under the renal capsule of males; controls received muscle. Three weeks later, all animals were given iv injecions of [³H]testosterone, and at various time intervals afterwards, the ventral, dorsal, and lateral prostate lobes were removed and analyzed for total [³H]testosterone and [³H]DHT. The presence of the grafts resulted in an increase in lateral lobe weight and protein content, while the ventral and dorsal lobes of the engrafted rats were not different from those in controls. The prostatic accumulation of the pulse radioactivity was rapid, and the excess levels of radioactivity declined quickly by 30–60 min. Elevated serum PRL did not alter the uptake pattern or levels of radioactivity in any of the prostate lobes. DHT constituted the majority of the tissue radioactivity, while testosterone comprised only a small percent. The relative levels of tissue testosterone and DHT in each of the three prostatic lobes were not influenced by the presence of pituitary grafts at any time point. The grafts were, however, associated with an increased disappearance rate of tissue [³H] DHT in the lateral lobe exclusively. It is suggested that the elevated serum PRL is responsible for increasing the turnover of DHT in the lateral lobe, and that this event is related to the increased growth in that lobe exclusively.