AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 1 1-12, Copyright © 1986 by American Physiological Society
Comparative facilitated transport of oxygen
J. M. Gonzalez-Fernandez and S. E. Atta
Numerical solutions were obtained for a model of facilitated transport of
O2. The dependence of the facilitated flow on the concentrations of O2 at
the two boundaries of the transport path was studied. The numerical values
of the parameters correspond to the adult Ascaris lumbricoides and to
vertebrate red striated muscle. A global control principle is formulated.
This states that for every fixed O2 concentration at the low concentration
boundary there exists an O2 concentration at the high concentration
boundary for which the facilitated flow is maximum. The collection of these
maxima makes possible the existence of a global adjustment of the
facilitated transport in contradistinction to the mere presence of a local
maximum. The ranges of the pairs of boundary O2 concentrations thus defined
and for which the facilitated flow is within 70% of its attainable maximum
were found to coincide with the physiological ranges of boundary O2
concentrations for the Ascaris and vertebrate striated muscle. This
phenomenon has the character of a graded compensatory mechanism to hypoxia.
It is an intrinsic property of the carrier transport system and does not
depend on sensors for hypoxia.
