THE EFFECT OF BA2+ ON THE NITRERGIC MECHANISM IN THE ISOLATED FROG LUNG PREPARATION

1. The present study was undertaken to investigate effects of Ba2+ on the isolated frog lung strips depolarized by 20 mM K+ in Ca2+ free Rin ger solution. 2. Ba2+ produced monophasic relaxant response, whereas C a2+ induced biphasic response consisting of a transient relaxation and a marked contraction. Both kinds of relaxation were inhibited complet ely by L-NOARG. L arginine reversed the action of L-NOARG. 3. Ferrous sulfate, pyrogallol, hydroquinone, and vanadate reduced the Ba2+-induc ed relaxation in a concentration-dependent manner. 4. These findings s uggest that Ba+-induced relaxation may fully be mediated by the nitrer gic mech anism and the effect of Ba2+ on the nitric oxide synthase may be more selective than Ca2+. (C) 1998 Elsevier Science Inc.