DNA synthesis in the canine prostate: Effects of androgen and estrogen treatment

Abstract

Canine prostatic DNA synthesis was evaluated by measuring [³H]thymidine incorporation into DNA of tissue slices in vitro. Among untreated beagles, prostatic DNA synthesis rates in young dogs with normal prostates, young dogs with spontaneous benign prostatic hyperplasia (BPH), and old dogs with BPH were 676 ± 186, 1,220 ± 156, and 641 ± 88 cpm/100 μg DNA/hr, respectively. Among 81 young beagles (intact or castrated) that had been treated for 4 months with various steroids, rates of DNA synthesis varied according to the type of hormonal treatment. Prostatic DNA synthesis (cpm/100 μg DNA/hr) was significantly different (P < 0.001) for dogs treated with estradiol alone (1,658 ± 221 cpm/100 μg DNA/hr; n = 10 dogs), androgen alone (testosterone, 5a‐dihydrotestosterone, or 5a‐androstane‐3a, 17β‐diol; 1,000 ± 61 cpm/100 μg DNA/hr; n = 40 dogs), or a combination of androgen plus estradiol (591 ± 49 cpm/100 μg DNA/hr; n = 31 dogs). However, there was no correlation between prostate size and rate of DNA synthesis (cpm/100 μg DNA/hr). Although treatment with estrogen alone resulted in the highest rate of DNA synthesis, it produced squamous metaplasia and the smallest prostates; these results are indicative of a high rate of cell turnover. Comparing prostates that reached the same size following 4 months of treatment with androgen alone or androgen plus estrogen, the rate of prostatic cell turnover was lower in the androgen plus estrogen group. These results are interpreted to indicate an inhibitory effect of estradiol on the rate of cell death in the presence of androgens.