THE ROLE OF VITAMIN-D IN NORMAL PROSTATE GROWTH AND DIFFERENTIATION

Although increasing data indicate a role for vitamin D in prostate can cer, little is known about the role of this hormone in the noncancerou s prostate. We examined the effect of 1,25-dihydroxyvitamin D-3 (1,25 D) on the growth of noncancerous rat prostates in vivo, Rats were cast rated and treated with vehicle (controls), 1,25 D, testosterone, or a combination of both hormones for 2 weeks. Histological examination of the harvested prostates revealed that 1,25 D had a selective regressiv e effect on epithelial cells in treated rats compared to untreated cas trated rats and to normal uncastrated rats. However, 1,25 D stimulated stromal growth in the prostate. The mean prostatic weight of the vita min D-treated rats was twice that of the untreated rats (0.13 +/- SEM 0.005 g versus 0.06 +/- SEM 0.006 g). The histological differences wer e less marked in the testosterone-supplemented animals. A greater degr ee of cellular differentiation was observed in the rats treated with t estosterone and vitamin D compared to rats that received testosterone supplementation alone. Studies of the nuclear matrix composition revea led differences between the testosterone-supplemented and the testoste rone and 1,25 D-treated rat prostates. We conclude that in the absence of testosterone, 1,25 D may exert a growth-promoting effect on the pr ostatic stroma in vivo. In concert with testosterone, it may play an i mportant role in the growth and differentiation of the normal rat pros tate.