Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle

Abstract

To examine the effects of vascular tone reduction on O2consumption of the vascular wall, we determined the O2consumption rates of arteriolar walls under normal conditions and during vasodilation induced by topical application of papaverine. A phosphorescence quenching technique was used to quantify intra- and perivascular Po2in rat cremaster arterioles with different branching orders. Then, the measured radial Po2gradients and a theoretical model were used to estimate the O2consumption rates of the arteriolar walls. The vascular O2consumption rates of functional arterioles were >100 times greater than those observed in in vitro experiments. The vascular O2consumption rate was highest in first-order (1A) arterioles, which are located upstream, and sequentially decreased downstream in 2A and 3A arterioles under normal conditions. During papaverine-induced vasodilation, on the other hand, the O2consumption rates of the vascular walls decreased to similar levels, suggesting that the high O2consumption rates of 1A arterioles under normal conditions depend in part on the workload of the vascular smooth muscle. These results strongly support the hypothesis that arteriolar walls consume a significant amount of O2compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O2to the surrounding tissue.