The kinetics of glucose transport through the human red cell membrane

Abstract

Because of the well-known deviations from predictions assuming penetration by simple diffusion, and the conflicting interpretations in the literature, the transport of glucose in both directions across the human red blood cell membrane was studied using improved osmotic methods. A kinetic analysis was carried out in two ways; (1) by graphical evaluation of the penetration rate as a function of substrate concentration ( differential method), (2) by testing the fit of experimental data to the integral equations representing the time course of penetration for various basic types of transport kinetics ( D, Z 1, Z 2, E) discussed previously ( integral method). Both methods of evaluation showed agreement with type E, characterized by the relation dS dt = v = K E[ 1 (S) i − 1 (S) 0 ] . The result is discussed with respect to the transport mechanism, particularly as regards special conditions of saturation. The values found for the constants K E differ for entrance (7 × 10 −2) and exit (4 × 10 −2). This result may point to additional elements of the transport.