Effects of neomycin on galactose absorption across rat jejunum.

The effects of neomycin sulphate on galactose absorption have been studied using in vivo and in vitro preparations of rat small intestine. Neomycin (10(-3)M) produced an increase in the maximum transport capacity (Jmax) for the active component of absorption in vivo. The apparent Kt for absorption was unaffected. The antibiotic caused a dose-dependent increase in the potential difference across the mucosal membrane (Vm) measured in vitro, a maximal effect being seen at a concentration of 10(-4)M. Furthermore, the magnitude of the depolarization induced by the addition of galactose (4 mM) to the mucosal fluid was enhanced by neomycin (10(-4)M). Phlorhizin (10(-4)M) abolished the galactose-induced depolarization in both the absence and presence of the antibiotic. It is concluded that neomycin increases the electrical driving force for Na+ during Na+-coupled galactose entry into the enterocyte.