Inhibition of active intestinal sugar transport by digitalis

Abstract

Ouabain or thevetin (10–5 m) inhibits the mucosal-to-serosal flux of 3-O-methylglucose only if present in the serosal but not if in the mucosal compartment. Digitoxin (10–4 m) inhibits if put in either compartment because it passes rapidly across the gut wall. The site of inhibition of the intestinal sugar pump thus is identical with that of the sodium pump. These findings support the theory that a functioning sodium pump is essential for the activation of the sugar pump in the small intestine, but they do not suggest a direct sodium effect on the sugar carrier.