Insulin Inhibits Low Oxygen-Induced ATP Release from Human Erythrocytes: Implication for Vascular Control

Objective: ATP released from human erythrocytes in response to reduced oxygen tension (pO2) participates in the matching of oxygen (O2) supply with need in skeletal muscle by stimulating increases in blood flow to areas with increased O2 demand. Here, we investigated the hypothesis that hyperinsulinemia inhibits ATP release from erythrocytes and impairs their ability to stimulate dilation of isolated arterioles exposed to decreased extraluminal pO2. Materials and Methods: Erythrocyte ATP release was stimulated pharmacologically (mastoparan 7) and physiologically (reduced pO2) in the absence or presence of insulin. We also examined the ability of isolated skeletal muscle arterioles perfused with buffer containing erythrocytes treated with insulin or its vehicle (saline) to dilate in response to decreased extraluminal pO2. Results: Insulin significantly attenuated mastoparan 7- and reduced pO2-induced ATP release. In vessels perfused with untreated erythrocytes, low extraluminal pO2 resulted in an increase in vessel diameter. In contrast, when erythrocytes were treated with insulin, no vasodilation occurred. Conclusions: These studies demonstrate that insulin inhibits ATP release from erythrocytes in response to reduced pO2 and impairs their ability to stimulate dilation of skeletal muscle arterioles. These results suggest that hyperinsulinemia could hinder the matching of O2 supply with need in skeletal muscle.