Metabolic suppression and oxygen availability

Abstract

The aerobic metabolic rates of cells, tissues, and even whole organisms remain relatively constant down to very low values (O2-regulating response) or decline steadily with O2 availability (O2-conforming response). (O2-regulating systems attempt to make up the energy deficit arising when O2 uptake begins to decline by activating anaerobic metabolism; this process is termed the Pasteur effect and typically involves 5- to 15-fold increases in glucose utilization rates. O2 conformers do not make up the energy deficit and thus enter a metabolically arrested state as O2 availability declines. Current data suggest that O2 conformers can maintain coupled metabolism–membrane functions at metabolically arrested states while O2 regulators cannot, presumably because of more permeable membranes and thus higher energy-dependent ion pumping requirements. These fundamental differences in response to, and tolerance of, hypoxia may be related to qualitative or quantitative differences in inducible stress proteins during O2 deprivation.