Endocytic uptake and vesicular transport of injected horseradish peroxidase in the vacuolar apparatus of rat liver cells

Abstract

Horseradish peroxidase (HRP) has been used as a cytochemical tracer to study peculiar ultra-structural aspects of exogenous protein uptake and fate in four types of rat liver cells. In all cell types HRP was adsorbed on the cell surface prior to endocytotic engulfment and sequestration within cytoplasmic particles. Most often, the pinocytotic vesicles ultimately acquired acid phosphatase activity thus becoming digestive vacuoles. In hepatocytes however, many of them seemed involved in diacytosis towards the bile canaliculi. The localization of HRP in cytoplasmic annular profiles and intercellular spaces is also described.