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

To examine the effects of vascular tone reduction on O₂ consumption of the vascular wall, we determined the O₂ consumption 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 PO₂ in rat cremaster arterioles with different branching orders. Then, the measured radial PO₂ gradients and a theoretical model were used to estimate the O₂ consumption rates of the arteriolar walls. The vascular O ₂ consumption rates of functional arterioles were > 100 times greater than those observed in in vitro experiments. The vascular O₂ consumption 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 O₂ consumption rates of the vascular walls decreased to similar levels, suggesting that the high O₂ consumption 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 O₂ compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O₂ to the surrounding tissue.