Galactose-specific receptor modulation related to the onset of apoptosis in rat liver

The expression of the asialoglycoprotein receptor of hepatocytes and the galactose-specific receptors of non-parenchymal liver cells during the onset of apoptosis in liver of rats treated with lead nitrate was studied. During the involution of lead nitrate-induced hyperplasia in rat liver (occurring at 5 days after the injection) a significant increase of asialoglycoprotein receptor (ASGP-R) expression on hepatocytes coincided with the massive death by apoptosis of the same cells. The increase in the receptor expression was sustained by a large increase in the level of its specific mRNA. As a consequence of lead nitrate injection, we also detected a drastic change of the galactose-specific receptor expression and distribution on the surface of rat liver sinusoidal cells. However, the modulation of the receptor expression on the Kupffer cells did not parallel that observed for the ASGP-R: the peak of surface expression measured on hepatocytes always followed the one observed on Kupffer cells. Our data show a first evidence of a receptor modulation during the process of apoptosis. In fact, the entire carbohydrate recognition system of the liver is modulated during the onset of apoptosis induced by lead nitrate injection, but the pattern of modulation depends on the cellular types. We suggest that a physiological role for the hepatic carbohydrate recognition systems is related to the apoptosis of liver.