GALACTOSE-SPECIFIC RECEPTOR MODULATION RELATED TO THE ONSET OF APOPTOSIS IN RAT-LIVER

The expression of the asialoglycoprotein receptor of hepatocytes and t he 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 incr ease 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 in jection, we also detected a drastic change of the galactose-specific r eceptor expression and distribution on the surface of rat liver sinuso idal 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 recepto r modulation during the process of apoptosis. In fact, the entire carb ohydrate recognition system of the liver is modulated during the onset of apoptosis induced by lead nitrate injection, but the pattern of mo dulation depends on the cellular types. We suggest that a physiologica l role for the hepatic carbohydrate recognition systems is related to the apoptosis of liver.