Abstract 5526: Maternal Smoking and Smoking Cessation in Early Pregnancy and Endothelium-Dependent Bradykinin-Mediated Relaxation of Uterine Small Arteries
Background - Impaired endothelium-dependent vasodilatation in pregnant smokers may reduce the uterine blood flow to the fetus and result in retarded fetal growth. The present study aimed at investigating endothelium-dependent bradykinin-mediated vasodilation in uterine small arteries from pregnant non-smokers, smokers, and ex-smokers who quitted smoking early in pregnancy.
Methods and Results - Of 29 healthy, singleton pregnancies scheduled for elective cesarean section; 12 were non-smokers, 9 were smokers, and 8 were ex-smokers. Serum cotinine verified self-reported smoking. Newborns of smokers were shorter and had a smaller head circumference compared to those of non-smokers (P<0.05), but newborns of ex-smokers were similar to those of smokers and non-smokers. Uterine arteries were dissected from myometrial biopsies and vascular function was assessed on a small vessel myograph for isometric recordings. Preconstricted arteries from non-smokers had a better bradykinin-induced relaxation than arteries from smokers and ex-smokers (P<0.05). In the presence of L-NG-nitroarginine (nitric oxide (NO) synthase inhibitor), arteries from smokers and ex-smokers did not relax to bradykinin, while arteries from non-smokers relaxed at high bradykinin concentrations (P<0.05). In the presence of L-NG-nitroarginine and indomethacin (cyclooxygenase inhibitor) arteries from non-smokers no longer responded to bradykinin. Relaxations to sodium nitroprusside (NO donor) were similar in arteries from non-smokers and smokers, but were better in arteries from ex-smokers (P<0.05).
Conclusions - The findings suggest that maternal smoking reduces endothelium-dependent bradykinin-mediated relaxation in uterine small arteries contributing to retarded fetal growth, and suggest that smoking cessation early in pregnancy does not abolish this effect, but improves smooth muscle sensitivity to NO.