The effect of Ba2+ on the nitrergic mechanism in the isolated frog lung preparation

PubMedID: 95952881. The present study was undertaken to investigate effects of Ba2+ on the isolated frog lung strips depolarized by 20 mM K+ in Ca2+ free Ringer solution. 2. Ba2+ produced monophasic relaxant response, whereas Ca2+ induced biphasic response consisting of a transient relaxation and a marked contraction. Both kinds of relaxation were inhibited completely by L-NOARG. L arginine reversed the action of L-NOARG. 3. Ferrous sulfate, pyrogallol, hydroquinone, and vanadate reduced the Ba2+-induced relaxation in a concentration dependent manner. 4. These findings suggest that Ba+-induced relaxation may fully be mediated by the nitrergic mechanism and the effect of Ba2+ on the nitric oxide synthase may be more selective than Ca2+