EFFECTS OF GLYCOSYLATED HEMOGLOBIN ON VASCULAR-RESPONSES IN-VITRO

Vascular responses to endothelium-dependent vasodilators are greatly i mpaired in vivo, while isolated blood vessels from animals with diabet es mellitus demonstrate less consistent degrees of impairment. Glycati on of proteins, such as hemoglobin, has been implicated in the vascula r abnormalities associated with diabetes. Objective: The purpose of th is study was to test the hypothesis that glycosylated hemoglobin is ca pable of reducing endothelium-dependent vasodilator responses, possibl y explaining impaired dilation observed in vivo. Methods: To test this hypothesis, the effect of glycosylated hemoglobin (GH) on vascular re sponses was studied in several vascular beds, including ventricular mi crovessels and coronary, mesenteric, femoral, and renal arteries. Coro nary arterioles were isolated and mounted between two glass pipettes i n a pressurized (30 cmH(2)O) organ chamber. Isolated artery segments w ere studied using a standard isometric ring technique. Results: In ven tricular microvessels, 10 nM nGH (non-GH) and GH both attenuated the r elaxation to Ach. A lower concentration, 1 nM nGH or GH, did not alter dilation to Ach. In coronary, femoral, mesenteric and renal artery se gments, endothelium-dependent responses were not altered by the presen ce of 10 or 100 nM nGH or GH. Conclusion: In coronary microvessels, an d coronary, femoral, mesenteric and renal arteries, GH is not responsi ble for the impaired endothelial function associated with diabetes mel litus.