Effect of glycosylated hemoglobin on endothelium-dependent relaxation of omental arteries from pregnant women, ,

Objective: This study was intended to test the hypothesis that glycosylated hemoglobin adversely affects endothelium-dependent vascular relaxation during pregnancy. Study Design: Omental artery rings (3 mm) obtained from patients undergoing cesarean delivery at term were suspended in organ chambers for isometric tension recording in Krebs bicarbonate solution. They were bubbled with 5% carbon dioxide in air (37°C, pH 7.4). After equilibration at 1-g passive tension and contraction with endothelin 1, concentration-relaxation curves in response to bradykinin were determined in the presence or absence of oxyhemoglobin, glycosylated hemoglobin, or nitric oxide synthase inhibitors (N ω-nitro-l -arginine methyl ester or N ω-nitro-l -arginine). Results: Oxyhemoglobin and glycosylated hemoglobin attenuated the endothelium-dependent relaxation induced by bradykinin. The inhibition did not differ significantly between the 2 nitric oxide scavengers and was of the same magnitude as that noted with the nitric oxide synthase inhibitors. Conclusion: Glycosylation of hemoglobin does not change its effect on endothelium-dependent relaxation in human omental vessels during pregnancy. These data do not support the hypothesis that glycosylated hemoglobin may be the reason for abnormal endothelial function in diabetes. (Am J Obstet Gynecol 1998;179:1047-50.)