PMID: 8945885Nov 1, 1996Paper

Regulation of oxygen diffusion in hypoxic isolated cardiac myocytes

The American Journal of Physiology
E Takahashi, K Doi

Abstract

In the normal beating heart, oxygen pressure (PO2) gradients between capillary blood and intracellular space are so large that cytosolic PO2 may decline to around PO2 at half saturation of myoglobin (2-5 Torr). Hence, a decrease in capillary blood PO2 of a few Torr would easily deplete oxygen in mitochondria if PO2 gradients are unchanged. The aim of the present study was to demonstrate, in a single isolated cardiac myocyte of the rat, a mechanism that reduces PO2 gradients in hypoxia so that oxygenation of the intracellular space would be sustained. Using a newly developed microspectrophotometric device, we were able to follow changes in cytosolic PO2 of an individual ventricular myocyte in an hypoxic medium. For extracellular PO2 of 4.4 Torr, we found an elevation (2.1 Torr) of the cytosolic PO2 when oxygen consumption of the cell was abolished by 2 mM NaCN, thus demonstrating PO2 gradients from extracellular medium to cytosolic space in a single individual cardiomyocyte. The magnitude of these PO2 gradients was reduced as extracellular PO2 was further lowered, and they were no longer detectable for extracellular PO2 of 0.6 Torr. To further elucidate physiological effects of the PO2-dependent changes in PO2 gradients demonstr...Continue Reading

Citations

Dec 21, 2000·American Journal of Physiology. Heart and Circulatory Physiology·J ZhangR J Bache

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