The Effects of Low O2 Supply on the Respiratory Activity, Reduced Pyridine Nucleotide Fluorescence, K+ Efflux and the Surface PO2 and PCO2 of the Isolated, Perfused Rat Liver
The problem of oxygen transport to tissue may be analyzed in terms of three main fluxes and their conjugate thermodynamic forces, namely the convectional flux of oxygen through the vascular network driven by the perfusion pressure, the diffusional flux of O2 from the capillary wall to the interior of cells driven by the PO2 gradient, and the flux of O2 through the redox chemical reaction network driven by the chemical affinity. Under physiological conditions, any one of the three fluxes will be affected by alterations in any one of the three forces. In the present study, we have investigated the metabolic and ionic effects of altering two of the three forces, the perfusion pressure at a constant arterial PO2 and the arterial PO2 at a constant perfusion pressure. The results obtained show that the main difference between “no flow” anoxia and “normal flow” anoxia (Kessler et al., 1974) involves a dramatic increase in the tissue PCO2 and the activity of extracellular K+ in the former but not in the latter. In addition, the extent of pyridine nucleotide reduction as judged from the NAD(P)H fluorescence increase is approximately twice as great in ischemia as in “normal flow” anoxia.
KeywordsPerfusion Pressure Supply Rate Pyridine Nucleotide Uptake Curve Fluorescence Increase
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