Comments |
"On intact human red cell membranes, the permeability [see [1] below], at the infinitesimal concentration, to D-glucose of 10^-5 to 4x10^-4 cm/sec has been estimated on the basis of kinetic analysis of the transport affinity (Km)
and the maximum rate (Vmax) (LeFevre & McGinniss, 1960 Miller, 1968
Jung, 1971)...[1]For sugars which are transported by a saturable path, a true permeability P cannot
be calculated. Permeability calculated at an infinitesimal concentration of the sugars,
where no saturation is effective, however, would provide a unique measure of relative
permeation by different permeants. This permeability at an infinitesimal concentration
of the permeant is obtainable by taking the first derivative of the classical Michaelis-
Menten expression of the carrier-mediated flux (Wilbrandt & Rosenberg, 1961) with
respect to the permeant concentration, at the condition of zero permeant concentration,
(Vmax/Km), then dividing by the total surface area of the cells. The values of 1.55x10^-6cm^2 and 8.7x10-11cm^3 were adopted for the surface area and the volume, respectively,
of a single human red cell (Whittam, 1964)." |