Distribution of an asialoglycoprotein receptor on rat hepatocyte cell surface.

Abstract

Direct ferritin immunoelectron microscopy was applied to visualize the distribution of the hepatocyte cell surface of the asialoglycoprotein receptor which is responsible for the rapid clearance of serum glycoproteins and lysosomal catabolism. For this purpose, rabbit antibody against the purified hepatic binding protein specific for asialoglycoproteins was prepared and coupled to ferritin by glutaraldehyde. The specific antibody conjugates were incubated with the hepatocytes, which were isolated from rat liver homogenate after fixation by glutaraldehyde perfusion. These cells preserved well the original polygonal shape and polarity, and it was easy to identify the sinusoidal, lateral, and bile canalicular faces. The surface density of the ferritin particles bound to the sinusoidal face was about four times higher than that of particles bound to the lateral face, while the bile canalicular face was hardly labeled and almost at the control level. Using the surface area of hepatocyte measured by morphometrical analyses, it was estimated that approximately 90% of bound ferritin particles were at the sinusoidal face, approximately 10% at the lateral face, and approximately 1% at the bile canalicular face. Nonhepatic cells such as endothelial and Kupffer cells had no receptor specific for asialoglycoproteins.