AJP - Cell Physiology, Vol 271, Issue 6 C2053-C2061, Copyright © 1996 by American Physiological Society

ARTICLES

Oxygen dependence of respiration in coupled and uncoupled endothelial cells

R. Steinlechner-Maran, T. Eberl, M. Kunc, R. Margreiter and E. Gnaiger
Department of Transplant Surgery, D. Swarovski Research Laboratory, University Hospital Innsbruck, Austria.

We studied the oxygen dependence of respiration in cultured human umbilical vein endothelial cells by use of high-resolution respirometry. The rate of oxygen consumption varied from 30 to 50 pmol O2.s-1.(10(6) cells)-1 over a sixfold range of cell densities. Respiration was stimulated up to 3.5-fold by uncoupling with carbonyl cyanide p-trifluoromethoxyphenylhydrazone or 2,4-dinitrophenol, and the PO2 at half-maximal respiration (P50) increased from 0.05 to 0.12 kPa (0.3 to 0.9 Torr) with respiratory rate. P50 decreased to a minimum of 0.02 kPa when uncoupled cells were inhibited to control levels. Differences in cell size explained a variation of approximately 0.015 kPa in P50 at similar respiratory rates per cell. Oxygen diffusion to mitochondria contributed maximally 30% to the regulation of P50 in coupled cells, as deduced from the shallow slope of the flux dependence of P50 in uncoupled-inhibited cells compared with the slope in coupled cells. Therefore 70% of the flux dependence of P50 in coupled cells was caused by changes in metabolic state, which correlated with respiratory rate.

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