Na+-dependent transport system for taurocholate in rat small intestine; Its localization in the terminal ileum and variation by fasting.

Abstract

The uptake of taurocholate in rat small intestine was investigated with everted sacs and epithelial cells. It was ascertained by means of these assay systems that Na+ -dependent taurocholate transport would be confined to the distal ileum. The effect of fasting on the Na+ -dependent taurocholate transport was assessed using isolated epithelial cells from there. Fasting for 2 days led to a considerable decrease in the taurocholate uptake by the epithelial cells regardless of Na+ -dependent or -independent transport. When kinetic parameters (Kt, Vmax) were obtained for net Na+ -dependent taurocholate transport from double-reciprocal plots of the taurocholate concentration against its corresponding transport rate, these values suggested that a diminution not in the affinity for taurocholate but in the quantity of "carrier" protein would have arisen from semi-starvation.