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

Abstract

雄家兎を3群に分け, 血中テストステロン測定後それぞれLH-RH analogue (leuprolide acetate 1.5mg/kg)の皮下注射をLH-RH群に, 精巣摘除術を精巣摘除群に, sham手術を対照群に施した.毎週血中テストステロンを測定し, 4週後に実験に供した.1週後血中テストステロン濃度はLH-RH群及び精巣摘除群で対照群に比べて有意に低下し, これはその後3週間持続した.実験浴槽内における遊離海綿体の各種刺激に対する反応性を調べた結果, LH-RH analogue投与により陰茎海綿体の収縮機能は変化しないものの, 電気刺激とsodium nitroprussideに対する弛緩反応が精巣摘除術同様に低下していた

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.