Effects of neomycin on galactose absorption across rat jejunum

1 The effects of neomycin sulphate on galactose absorption have been studied using in vivo and in vitro preparations of rat small intestine. 2 Neomycin (10−3m) produced an increase in the maximum transport capacity (Jmax) for the active component of absorption in vivo. The apparent Kt for absorption was unaffected. 3 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 −4m. Furthermore, the magnitude of the depolarization induced by the addition of galactose (4 mm) to the mucosal fluid was enhanced by neomycin (10−4m). Phlorhizin (10 −4m) abolished the galactose-induced depolarization in both the absence and presence of the antibiotic. 4 It is concluded that neomycin increases the electrical driving force for Na+ during Na+-coupled galactose entry into the enterocyte.