Competitive kinetics in the inhibition of sugar intestinal transport by phlorizin, in vivo

Abstract

Kinetics of sugar transport inhibition by phlorizin in rat intestine has been studied in vivo.Jejunum lumen was perfused during a series of successive 1 minute periods of absorption.Total sugar absorption was assumed to be the sum of a mediated transport component plus a passive one persisting in the presence of 5 X 10(-4) M phlorizin.The values of transport rates, corrected in this way, showed Michaelis-Menten kinetics and proved that inhibition of D-glucose, D-galactose and 6-deoxy-D-glucose transport by low concentrations of phlorizin (5 X 10(-06) M) displays a typical competitive kinetics (apparent Ki = 4-10 X 10(-06) M) as had been long before reported from in vitro experiments.