PREGNANCY AUGMENTS NITRIC OXIDE-DEPENDENT DILATOR RESPONSE TO ACETYLCHOLINE IN THE HUMAN UTERINE ARTERY

The influence of pregnancy on the dilator effects of acetylcholine in the isolated human uterine artery was investigated. Acetylcholine (0.1 nM to 0.1 mu M) produced concentration-and endothelium-dependent rela xation of norepinephrine (3 mu M)-induced contraction, The relaxation was greater in arteries from pregnant patients (P arteries) than from non-pregnant patients (NP arteries). The maximal relaxation was 53.5 /- 3.4% (n = 21) in P arteries and 23.5 +/- 2.5% (n = 35) in NP arteri es. In both P and NP arteries the cholinergic relaxation was increased in the presence of superoxide dismutase and greatly reduced in the pr esence of the nitric oxide synthase inhibitors, N-G-mono-methyl L-argi nine (L-NMMA) and L-nitro-arginine-methylester (L-NAME). The effect of these nitric oxide synthase inhibitors was reversed by L-arginine. We conclude that pregnancy enhances acetylcholine-induced nitric oxide s ynthesis and release in the human uterine artery.