Predominant role for nitric oxide in the relaxation induced by acetylcholine in human uterine artery.

The effect of acetylcholine on the isolated human uterine artery rings was investigated. Acetylcholine (10(-10) M to 6 x 10(-5) M) induced concentration- and endothelium-dependent relaxation (pD2 = 7.4 +/- 0.02, maximal response was 77.5 +/- 6.3% of relaxation induced by papaverine at 3 x 10(-4) M) of the pre-contracted arterial segments. Indomethacin (10(-5) M), diethylcarbamazine (10(-4) M) and tetra-ethylammonium (3 x 10(-4) M) had no effects on acetylcholine-evoked relaxation. Methylene blue (10(-5) M) and NG-monomethyl-L-arginine (L-NMMA) (3 x 10(-6) to 3 x 10(-5) M) antagonized relaxation induced by acetylcholine. The inhibition of endothelium-dependent relaxation by L-NMMA (10(-5) M) was reversed by L-arginine (10(-5) M) but not by D-arginine (10(-4) M). It is concluded that in uterine artery acetylcholine induces endothelium-dependent relaxation of isolated uterine artery is probably mediated via endothelial nitric oxide formation.