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

Abstract

This study was intended to test the hypothesis that glycosylated hemoglobin adversely affects endothelium-dependent vascular relaxation during pregnancy. 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 degrees 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(omega)-nitro-L-arginine methyl ester or N(omega)-nitro-L-arginine). 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. 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.