Effect of monensin on fluid phase and receptor mediated endocytosis by rat hepatocyte monolayers

We have investigated the effect of monensin on the uptake of sucrose and sucrose-asialofetuin by rat hepatocyte monolayers and on the intracellular traffic of these molecules. Endocytosis of sucrose is not affected by monensin while that of sucrose-asialofetuin is markedly inhibited. Monensin causes a decrease of galactosyltransferase, a Golgi membrane enzyme without affecting dipeptidylpeptidase IV a plasma membrane enzyme and three lysosomal hydrolases. The inhibition of sucrose-asialofetuin uptake is proportional to the reduction of galactosyltransferase activity. Differential and isopyenic centrifugation results indicate that monensin at a concentration (10 μmol/I) that markedly decreases sucrose-asialofetuin uptake does not prevent the transfer of sucrose and sucrose-asialofetuin from endosomes to lysosomes.