Characterization of the Independent and Combined Vasoactive Abilities of Hydrogen Ion and Carbon Dioxide in Skeletal Muscle Microvasculature
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Abstract
Hydrogen ion (H+) and carbon dioxide (CO2) are products of skeletal muscle metabolism and have been implicated in the hyperaemic response to muscle contraction. The microvasculature is instrumental to the increase in blood flow during contraction and its distribution to active fibers. To investigate the vasodilatory ability of H+ and CO2 separately on the skeletal muscle microvasculature, Tris(hydroxymethyl)aminomethane (TRIS) buffer was substituted for bicarbonate buffer and increasing concentrations/pressures of H+, CO2 and H+ with CO2 were applied to the cremaster muscle. 100.0 nmol/L H+, 60.7 mmHg CO2, and 60.7 mmHg CO2 with 158.5 nmol/L H+ induced 9.5 ± 1.9, 10.4 ± 3.1 and 7.6 ± 2.5 µm vasodilations respectively. Micropipette application of H+ and CO2 independently and combined onto arterioles and capillaries did not induce upstream arteriolar vasodilation. Thus, H+ and CO2 independently and combined are weak vasodilators that do not stimulate capillaries or arterioles to conduct vasodilation.