Oxygen dependence of respiration in coupled and uncoupled endothelial cells.
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.
Steinlechner-Maran
R
R
Department of Transplant Surgery, D. Swarovski Research Laboratory, University Hospital Innsbruck, Austria.
Eberl
T
T
Kunc
M
M
Margreiter
R
R
Gnaiger
E
E
D015687:Cell Hypoxia; D048429:Cell Size; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
D010100:Oxygen