Nonadrenergic, noncholinergic relaxation of human isolated corpus cavernosum induced by scorpion venom

Objectives, To examine the effects of Tityus serrulatus scorpion venom (TSV ) on human corpus cavernosum (HCC) using a bioassay cascade. Priapism is oc casionally observed in scorpion envenomation, mostly in children. Methods. HCC strips were suspended in a cascade system and superfused with aerated and warmed Krebs' solution at 5 mL/min. Noradrenaline (5 mu mol/L) was infused to induce a submaximal contraction of the HCC strips. The relea se of cyclooxygenase products was prevented by infusing indomethacin (6 mu mol/L). Results. N-omega-nitro-L-arginine methyl ester (10 mu mol/L; n = 10) increa sed the tone of the preparations and significantly reduced (P <0.01)the ace tylcholine (ACh) and TSV-induced relaxations. Subsequent infusion of L-argi nine (300 <mu>mol/L) partially reversed the increased tone and significantl y restored the relaxations induced by TSV and ACh (P <0.01). The soluble gu anylyl cyclase inhibitor ODQ (10 <mu>mol/L; n = 8) markedly reduced (P <0.0 1) the relaxations induced by TSV, ACh, glyceryl trinitrate, and bradykinin . 7-Nitroindazole (10 <mu>mol/L; n = 8) inhibited the relaxations induced b y TSV by 84% (P <0.01) and also caused small, but significant, reductions i n the ACh and bradykinin-induced HCC relaxations (P <0.05). Atropine (1 mu mol/L; n = 6) abolished the relaxations evoked by ACh (P <0.01), but had no effect on those elicited by TSV. Tetrodotoxin (1 <mu>mol/L; n = 6) abolish ed the relaxations induced by TSV (P <0.01) and also reversed the establish ed TSV-induced relaxation (n = 4). Conclusions, Our results indicate that TSV relaxes HCC through the release of nitric oxide from nonadrenergic, noncholinergic (NANC) nerves. The eluci dation of the mechanism responsible for the TSV-induced relaxations might b e useful for a better understanding of the development of priapism in cases of scorpion envenomation. UROLOGY 57: 816-820, 2001. (C) 2001, Elsevier Sc ience Inc.