The mechanisms of peroxynitrite-induced relaxations in isolated rat anococcygeus muscle.

We have previously reported that peroxynitrite (ONOO(-)) caused relaxations on isolated rat anococcygeus muscle and in the present study the possible mechanisms of the relaxant effect were investigated. ONOO(-) (0.03- 1.0 mmol/l)-induced relaxations were reduced significantly by the presence of an ATP-sensitive potassium channel (K(+)(ATP) channel) blocker, glibenclamide (0.3 micromol/l), or 1H-(1,2,4)oxadiazolo(4,3-alpha)quinoxalin-1-one (ODQ) (30.0 micromol/l), a guanylyl cyclase inhibitor. However, 3-aminobenzamide (3.0 mmol/l), an inhibitor of poly(ADP- ribose)synthase, did not influence the relaxant effect of ONOO(-) (1.0 mmol/l). Results of the present study implicate that activation of K(+)(ATP) channels and/or cGMP/K(+)(ATP) channel interaction might play a role in the relaxant responses to ONOO(-) in isolated rat anococcygeus muscle.