Effects of luteinizing hormone-releasing hormone (LH-RH) analogue on the function of the isolated rabbit corpus cavernosum.

An adverse effect of the administration of luteinizing hormone-releasing hormone (LH-RH) analogue is impotence. The effects of LH-RH analogue injection on the function of the rabbit corpus cavernosum were investigated. Eighteen male rabbits were divided into three groups, i.e., LH-RH analogue injection, castration, and sham-operated control groups. After measurement of serum testosterone, the LH-RH analogue (1.5 mg/kg leuprolide acetate) was injected once in the LH-RH group, castration in the castrated group, and sham surgery in the control group. Four weeks later, the rabbits were maintained in the same circumstance and serum testosterone was measured once a week. Four weeks after preparation, all rabbits were used for in vitro experiments. At one week the serum testosterone level of the LH-RH and castrated groups decreased significantly from that in the sham-operated control group, which was sustained for the next 3 weeks. Although contractile strength of the corporal tissue taken from the castrated group was weakened in response to phenylephrine and KCl, corporal contractile strength of the LH-RH group was not. Under precontraction with 200 microM phenylephrine relaxation of the corpus cavernosum in response to field stimulation and sodium nitroprusside significantly decreased in both the LH-RH and castrated groups. However, there were no differences in the maximal relaxations induced by ATP and bethanechol between the three groups. In conclusion, the LH-RH analogue impaired the relaxation of the corpus cavernosum induced by field stimulation and sodium nitroprusside as much as castration did. Although the corporal contraction to phenylephrine and KCl was decreased by castration, it was not altered by the LH-RH analogue.