Receptor-mediated endocytosis of enterokinase by rat liver: Preliminary characterisation of low-density endosomes

摘要: Abstract The endocytosis of enterokinase by rat hepatocytes has been studied both in a perfused liver system and the intact, anaesthetised animal. 10 min after administration enzyme, only 70% activity was cleared liver, whereas clearance total intact In cases, about 85% internalised enzyme co-purified with smooth microsomes virtually all (more than 90%) catalytic latent could be detected presence detergent. After min, 22.5% remained sinusoidal plasma membrane case while for animal this figure 10%, confirming more efficient Further subcellular fractionation showed that 8% associated low-density Golgi-like endosomal compartment (prepared from mitochondrial pellet), corresponding value 2.5%. Enterokinase specific also up to 50-times greater endosomes prepared A second (purified microsomes) contained enterokinase, which together derived mitochondria accounted 20% its passage through these two compartments shown not synchronous peripheral (sinusoidal membrane) internal (smooth microsomes). There were qualitative differences marker enzymes polypeptide composition between microsome-derived endosomes. sub-fractionation fractions on shallow sucrose gradients revealed complex heterogeneity within fractions. an apparent density-dependent separation galactosyltransferase asialoglycoprotein receptor coincident marked changes membranes, particularly 30–45 kDa range.