BAFILOMYCIN A1, A SPECIFIC INHIBITOR OF VACUOLAR-TYPE H-ATPASES, INHIBITS THE RECEPTOR-MEDIATED ENDOCYTOSIS OF ASIALOGLYCOPROTEINS IN ISOLATED RAT HEPATOCYTES()

Background/Methods: The role of vacuolar type H+-ATPases (v-ATPases) a nd pH gradient between the endocytic compartments and cytoplasm in the endocytosis of asialoglycoproteins was morphologically investigated i n isolated rat hepatocytes using bafilomycin A1, a specific inhibitor of v-ATPases. Results: Fluorescent staining by acridine orange showed that bafilomycin A1 inhibited the acidification of the endocytic compa rtments, Uptake of gold-conjugated asialofetuin was significantly inhi bited by bafilomycin A1, However, bafilomycin A1 did not significantly inhibit uptake of a fluid phase market; horseradish peroxidase. The n umber of autophagic vacuoles increased after the bafilomycin A1 treatm ent, However, materials in the autophagic vacuoles were rapidly degrad ed after the removal of bafilomycin A1. Conclusions: Results suggest t hat: (a) v-ATPases are necessary for acidification of the endocytic co mpartments; (b) the pH gradient between the endocytic compartments and the cytoplasm which is generated by v-ATPases is necessary for the re ceptor-mediated endocytosis of asialoglycoproteins, and (c) v-ATPases may contribute to the degradation of the materials in autophagic vacuo les.