POSSIBLE ROLE FOR ENDOTHELINS IN PENILE ERECTION

The effects of endothelins (endothelin-l and endothelin-3) on penile e rection were studied in vivo in the pithed rat. Penile erectile respon ses were evaluated by measurements of intracorporal pressure via a nee dle inserted into one corpus cavernosum. Injection of endothelins (0.1 -10 mu g/kg i.v.) was followed by a rapid rise in corporal pressure. T he responses to endothelin-l and endothelin-3 were equivalent at the l ower doses, but at 10 mu g/kg the response to endothelin-3 was greater than that to endothelin-l. NG-Nitro-L-arginine methyl ester (20 mg/kg ) but not indomethacin (10 mg/kg) antagonized the rise in corporal pre ssure caused by submaximal doses of endothelins. Electrical nerve stim ulation-induced increase in corporal pressure was reduced after 5 mu g /kg endothelin-l but not after the same dose of endothelin-3. The resu lts indicate that in corporal vasculature endothelin-3 has a predomina ntly vasodilator effect, while endothelin-1 has a vasodilator effect a t lower doses and a vasoconstrictor effect at higher doses. The vasodi lator action of endothelins is probably mediated by activation of endo thelin ET(B) receptors and local release of nitric oxide. Thus, endoth elins may participate in initiation and/or maintenance of penile erect ion.