The uptake of radioiodinated 5 alpha-dihydrotestosterone by the prostate of intact and castrated rats.

Radioiodinated steroid 2 alpha-125I-dihydrotestosterone was prepared by direct labeling procedure and subsequently utilized in the distribution studies on Albino Wistar male rats. Maximum radioactivity in the prostate was found 3 h after the administration of the radiolabeled steroid to 24-h castrated animals (1.29%/g wet weight) and to intact rats (0.57%). The pretreatment of animals with dihydrotestosterone yielded lower uptake by the prostate (0.29%-0.30%), epididymis, and testis while it did not influence the distribution in other androgen-insensitive tissues. The carbon-iodine bond was proved to be intact in the radiopharmacon examined and in its metabolites when retained by the rat prostate. The reported results are in line with our previous investigations on in vitro binding of radioiodinated dihydrotestosterone to androgen receptors but indicate also little utility of the same label for the visualization of the prostate gland.