[Electron microscopic study of horseradish peroxidase pinocytosis by white rat peritoneal macrophages in vivo].

Pinocytic activity of rat peritoneal macrophages has been studied morphometrically at the ultrastructural level, 1.5-50 minutes following the intraperitoneal administration of horseradish peroxidase at varying concentrations. Internalization of the tracer was carried out by relatively large vacuoles and coated microvesicles. A probable mechanism underlying the two structurally distinct kinds of pinocytosis by macrophages is discussed.