The effects of castration on relaxation of rat corpus cavernosum smooth muscle in vitro /

Abstract

This study was conducted to investigate the role oftestosterone in regulating the relaxation of isolated rat corpus cavernosum strips in vitro. Male rats were divided into treatment groups of intact, castrate, and castrate with testosterone replacement. Norepinephrine was added to contract each of the tissue strips. Next, sodium nitroprusside, experiment I, or 8-bromo-cGMP, experiment II, was added to relax the cavernosum tissue. Percent relaxations were recorded for each treatment group at each dose level. Sodium nitroprusside was added to the norepinephrine -4 -3 contracted tissues in doses of 10 and 10M. In this experiment, castration significantly reduced tissue responsiveness to sodium nitroprusside and testosterone replacement restored the response to intact levels. In the second experiment 8-bromo-cGMP was added to the -5 -4 norepinephrine contracted tissues in doses of 10 and 10M. 8-bromo-4 cGMP 10Mwas significantly less effective in relaxing tissue from castrate animals as compared to intact controls. Again, testosterone treatment restored the response to intact levels. Our results show a clear role of testosterone in regulating the ability of corpus cavemosum tissue to relax when treated with sodium nitroprusside or 8-bromo-cGMP in vitro. In addition, the data suggests that testosterone regulates sites distal to the formation of cGMP in this smooth muscle relaxation pathway.