Submitted on August 17, 2004
Accepted on January 19, 2005
Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle
Masahiro Shibata1*, Shigeru Ichioka1, and Akira Kamiya1
1 Department of Biomedical Engineering, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
* To whom correspondence should be addressed. E-mail: shibatam{at}m.u-tokyo.ac.jp.
To examine the effects of reducing vascular tone on the O2 consumption of the vascular wall, we determined the O2 consumption rates of arteriolar walls under normal conditions and during vasodilation induced by a topical application of papaverine. A phosphorescence quenching technique was used to quantify the intra- and perivascular pO2 values in rat cremaster arterioles having different branching orders. Using the measured radial pO2 gradient values, and a theoretical model, the O2 consumption rates of the arteriolar walls were then estimated. We found that the vascular O2 consumption rates of functional arterioles were more than 100 times greater than those seen in in vitro experiments. The vascular O2 consumption rate was highest in first order arterioles (1A), which are located upstream, sequentially decreasing downstream in 2A and 3A arterioles under normal conditions. During vasodilation induced by papaverine, on the other hand, the O2 consumption rates of the vascular walls all 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 as 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.
