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Chronic hyperglycemia impairs functional vasodilation via increasing thromboxane-receptor-mediated vasoconstriction

Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi

Submitted 12 June 2006 ; accepted in final form 1 August 2006

Individuals with hyperglycemia exhibit impaired exercise performance and functional vasodilatory response. Based on the importance of arachidonic acid (AA) metabolites in functional vasodilation and the increased thromboxane-to-prostacyclin ratio in diabetes, we hypothesized that chronic hyperglycemia in diabetes increases thromboxane-receptor (TP)-mediated vasoconstriction, resulting in an attenuated functional vasodilation. Three groups of lean Zucker rats (8 wk) were used to test the effects of chronic hyperglycemia on endothelial function: normal, streptozotocin (STZ; 70 mg/kg ip), and STZ + insulin (2 U/day). After 4 wk of treatment, spinotrapezius arcade arterioles were chosen for microcirculatory observation. Arteriolar diameter was measured following muscle stimulation and 10 µM AA application in the absence and presence of 1 µM SQ-29548 (TP antagonist). STZ rats exhibited significantly higher fasting glucose levels and attenuated functional and AA-induced dilation compared with normal animals. SQ-29548 improved the vasodilatory responses in STZ rats but had no effect in controls. Insulin treatment normalized both the glucose levels and the vasodilatory responses, and SQ-29548 treatment had no effect on functional or AA-mediated vasodilation in STZ + insulin animals. These results suggest that the impaired functional vasodilation in diabetic rats is due to hyperglycemia-mediated increases in TP-mediated vasoconstriction.

arachidonic acid; prostacyclin; diabetes

This article has been cited by other articles:

				L. Xiang, J. Dearman, S. R. Abram, C. Carter, and R. L. Hester Insulin resistance and impaired functional vasodilation in obese Zucker rats Am J Physiol Heart Circ Physiol, April 1, 2008; 294(4): H1658 - H1666. [Abstract] [Full Text] [PDF]