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

Abstract

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