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

The effect of acetylcholine on the isolated human uterine arteryrings was investigated. Acetylcholine (10^–10 M to 6x 10^–5M) induced concentration- and endothelium-dependent relaxation(pD2=7.4±0.02, maximal response was 77.5±6.3%of relaxation induced by papaverine at 3x10–4 M), diethylcarbamazine(104 M) and tetra-ethylammonium (3x10^–4 M) had no effectson acetylcholine-evoked relaxation. Methylene blue (10–5M) and NG-monomethyl-L-arginine (L-NMMA) (3x10^–6 to 3x10^–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) butnot by D-arginine (10^–4 M). It is concluded that in uterineartery acetylcholine induces endothelium-dependent relaxation.It is suggested that the acetylcholine-induced relaxation ofisolated uterine artery is probably mediated via endothelialnitric oxide formation