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× 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 3×10−4 M), diethylcarbamazine (10∼4 M) and tetra-ethylammonium (3×10−4 M) had no effects on acetylcholine-evoked relaxation. Methylene blue (10−5 M) and NG-monomethyl-L-arginine (L-NMMA) (3×10−6 to 3× 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. It is suggested that the acetylcholine-induced relaxation of isolated uterine artery is probably mediated via endothelial nitric oxide formation