Myoglobin content and oxygen diffusion: model analysis of horse and
steer muscle.
Conley, Kevin E., and Cliff Jones.
Department of Radiology and the Center for Bioengineering,
University of Washington Medical Center, Seattle, WA 98195-7115
APStracts 3:0217C, 1996.
We test the hypothesis that myoglobin is important for oxygen supply
near the oxidative capacity of muscle. This hypothesis is evaluated
using a simple model that incorporates the properties of heart and
skeletal muscle tissue taken from steers and horses exercising at
their maximum oxygen consumption rate. These tissue samples allowed
us to set the bounds on oxidative demand and O2 flux from red cell to
the core of the muscle fiber, to estimate the blood and tissue
capacities for O2 diffusion, and to define the capillary blood PO2
driving this O2 flux. A model combining blood convection with tissue
diffusion indicates that O2 diffusion alone is insufficient to
achieve the measured O2 fluxes in many samples. The myoglobin content
of these fibers is significantly correlated with this O2 diffusion
limitation and provides sufficient additional O2 flux to meet muscle
O2 demand. The presence of myoglobin maintains the PO2 in the fiber
core above anoxic levels for the majority of muscles. Thus myoglobin
is critical to O2 supply at fluxes near the maximum and prevents
anoxia by maintaining PO2 above levels needed to support
mitochondrial function.
Received 10 January 1996; accepted in final form 24 June 1996.
APS Manuscript Number C11-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996