Effect of Testosterone on the Relaxation of Rabbit Corpus Cavernosum

Kim, Jong Ki; Choi, Young Deuk; Chung, Woo Sik; Hong, Jae Yup; Park, Yong Yo; Choi, Hyung Ki

Abstract

Androgen was thought to be linked to sexual activity in man but it did not identify the peripheral action and its mechanism of androgen. The present study was designed to determine the role of testosterone in the relaxation of the corpus cavernosum. Effect of testosterone on the relaxation of rabbit corpus cavernosum was investigated from three groups of rabbit; two groups were castrated and the third underwent a sham operation (control). After castration, one group, received subcutaneous injection of testosterone (testosterone propionate 10 mg/day). Strips of rabbit corpus cavernosum were isolated and mounted in 10 ml organ chambers. Isometric tension measurement of acetylcholine (Ach: 10(-5)M) and papaverine (10(-5)M) in the precontracted cavernosal muscle strips with phenylephrine (5 x 10(-6)M) were performed in all groups; control, castration group (four sub-groups: 1, 2, 4 and 8 weeks after castration) and testosterone replacement group (four sub-groups: testosterone was given from 1, 2, 4 and 8 weeks after castration for 14 days respectively). The relaxation response of corpus cavernosal muscle to acetylcholine and papaverine was significantly decreased in castrated group and restored up to the level of control after testosterone replacement. The maximum inhibitory effect of castration on the relaxation of corpus cavernosal muscle began to be shown at 4 weeks after castration. Based on these results, we conclude that testosterone regulates the tone of cavernosal smooth muscle through the pathway including cholinergic endothelium mediated relaxation.