Effect of aging, castration, and testosterone administration on ribonuclease and ribonuclease-inhibitor activities in the prostate of rats

Free ribonuclease (RNase)-inhibitor activities in both ventral and dorsal prostates had their highest peaks in 4-week-old rats and smallest peaks in around 7-week-old animals. Total RNase activity in the ventral prostate decreased overall with age, while that in the dorsal prostate increased. No significant amount of free RNase activity was found in either prostate. Weight, protein content, and free RNase-inhibitor activity in both prostates decreased after castration and increased after administration of testosterone to castrated rats. Total RNase activity in the ventral prostate was increased by castration and decreased by testosterone administration. In the dorsal prostate, total RNase activity had two peaks, 7 d after castration and 2 d after testosterone administration. A large amount of free RNase activity was found in the ventral prostate 7 d after castration and this activity was decreased by testosterone administration. In the dorsal prostate, free RNase activity was not detected after castration and testosterone administration. These results suggest that changes in the level of RNase-inhibitor in both prostates are involved in the regulation of their RNA content through the control of free RNase activity.