Sodium and Sugar Fluxes across the Mucosal Border of Rabbit Ileum

Unidirectional influxes of sugars and Na from muscosal solution into the cells of rabbit ileum have been examined. The influxes of glucose, galactose, and 3-0-methyl glucose (3 MG) follow Michaelis-Menten type kinetics and are markedly dependent on the presence ofNa in the mucosal solution. For 3 MG, reduction of Na concentration causes a decrease in maximal rate of influx and little change in the "apparent Michaelis constant." There appeared to be little mediated entry of 3 MG into the cells from Na-free solution. The influx of Na was increased by the presence of 3 MG in the mucosal solution and at all Na concentrations tested, there was a 1:1 ratio between sugar influx and the sugar-dependent Na influx. On the basis of these observations, a model has been developed for the sugar transport system involving a transport site that combines with both sugar and Na.