L-NG-NITRO ARGININE INHIBITS NONADRENERGIC, NONCHOLINERGIC RELAXATIONS OF GUINEA-PIG ISOLATED TRACHEAL SMOOTH-MUSCLE

The effects of L-N(G)-nitro arginine (L-NOARG) on α-chymotrypsin-resistant, non-adrenergic, non-cholinergic (NANC) relaxations of guinea-pig tracheal smooth muscle have been examined. L-NOARG (1-100 μM), but not D-NOARG (100 μM), inhibited the NANC relaxations in a concentration-related manner. The effects of L-NOARG were partially reversed by L-arginine but not D-arginine. L-NOARG was without effect on acetylcholine-induced contractile responses of the trachea or on relaxations produced by vasoactive intestinal peptide, sodium nitroprusside or isoprenaline. These results suggest that an endogenous nitrate may contribute to NANC relaxations of tracheal smooth muscle.