ON THE MULTIPLICITY OF GLUCOSE ANALOGS TRANSPORT-SYSTEMS IN RAT INTESTINE

A study has been made to test if in intact epithelium of rat jejunum w ith in vivo and in vitro techniques, two transport systems for glucose and analogues, as those characterized in brush border membrane vesicl es from guinea pig jejunum, are operative. The passive and mediated tr ansport components of the D-galactose and methyl alpha-D-glucopyranosi de intestinal absorption and the mutual inhibitions between both subst rates at different relative concentrations have been measured. The eff ects of cytochalasin B and low temperature (20-degrees-C) on the trans port in vitro have also been observed. Cytochalasin B inhibits galacto se and alpha-methylglucoside transport at 0.1 and 40 mM concentrations in similar percentage. Transport of 0.1 and 40 mM galactose is inhibi ted 61 and 77 % respectively by low temperature (20-degrees-C). The tr ansport of galactose and alpha-methylglucoside could be explained by t he assumption of just one transport system shared by both substrates, with a higher affinity for alpha-methylglucoside. Operation of two sys tems was not demanded by the results, due perhaps to species specifici ty or to the distorting action of the unstirred water layers.