Measurements of Oxygen Flux from Arterioles Imply High Permeability of Perfused Tissue to Oxygen
A mathematical model developed for the analysis of oxygen flux from an arteriole surrounded by perfused tissue was used to analyze experimental data in the resting hamster cheek pouch retractor muscle. The flux predicted by the model, with the commonly accepted values of tissue permeability to oxygen (the Krogh diffusion coefficient), was an order of magnitude smaller than the average value of experimentally observed oxygen flux. The values of permeability required by the model to equate the predicted and observed oxygen flux are one to two orders of magnitude higher than the accepted values. Also, the values of the oxygen tension gradient in the arteriolar wall predicted by Fick’s law are an order of magnitude greater than the measured values reported in the literature. Since the accepted values of permeability are based on experiments with unperfused tissue and the values predicted by the model are for blood-perfused tissue, we conjecture that tissue permeability is a function of the perfusion conditions. Hence, there is a need for re-examination of the distribution of resistance to oxygen transport along the pathway between red blood cells and mitochondria. Theoretical estimates based on accepted values of tissue permeability to oxygen show resistances to oxygen transport inside and outside the capillaries to be of similar magnitude. However, if the tissue component of the resistance is significantly reduced because of greater permeability, the intracapillary resistance becomes dominant and is responsible for most of the drop in the oxygen tension between the red blood cells and the tissue.
KeywordsOxygen Tension Oxygen Transport Oxygen Flux Retractor Muscle Hemoglobin Oxygen Saturation
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