Abstract

Various sugars were administered intravenously to rabbits and the rate of exsorption from plasma to intestinal lumen was measured. The exsorption rates of lactulose, mannose, and xylose were directly related to their plasma concentration but varied according to their molecular weight. Wglucose and galactose did not appear in the intestinal lumen until very high plasma concentrations were reached. The mucosal barrier which prevented glucose and galactose exsorption was abolished when luminal phlorizin M times 10-minus 2 or another actively absorbed sugar was placed in the lumen. 2:4 Dinitrophenol M times 10-minus 3 and the absence of the sodium ion did not impair the ffficiency of the barrier. When the plasma glucose concentration was raised to very high levels, glucose began to appear in the lumen; further increases in the glucose concentration then produced a rapid exsorption of glucose.