d-Glucose balance in the enterocyte of rat jejunum "in vitro".

An everted sac of male albino rat jejunum (Wistar strain) incubated "in vitro" in used. Net d-glucose and Na+ transport together with d-glucose concentration in the emerging fluid [5], or in ths serosal fluid, and in the enterocytes are determined. Cell d-glucose concentration does not change significantly in a range between 20-200 mumoles or between 50-500 mumoles of net d-glucose transepithelial transport, depending on the experimental conditions. As far as cellular d-glucose and Na+ concentration is concerned, the enterocyte behaves as an homeostatic system. The mechanism involved in d-glucose extrusion is extensively discussed. Two hypothesis seem to be possible. First, the mechanism is an active metabolically dependent one, just as it is for sodium transport. Second, the metabolic activity favours d-glucose facilitated permeability through the basolateral membrane in such a way as to maintain a constant relationship between d-glucose and Na-extrusion, notwithstanding the fact that d-glucose concentration gradient across the basolateral membrane lowers by increasing Na and glucose extrusion rate.