Receptor-mediated clearance of tissue kallikreins by rat liver

The exsanguinated, isolated and perfused rat liver clears from the perfusate, at comparable rates, some native tissue kallikreins: human and horse urinary as well as hog pancreatic; the clearance rates were dependent on the initial enzyme concentration in the perfusing fluid. Contrary-wise, rat urinary kallikrein was cleared at negligible rates. Neuraminidase pretreatment of these four kallikreins did not alter their clearance rates. Horse urinary kallikrein binding to isolated prefixed hepatocytes was calcium-dependent and inhibited by asialofetuin (but not by fetuin) and some sugars; these characteristics are compatible with the interpretation that this native tissue kallikrein is recognized by the hepatocyte asialoglycoprotein-receptor. It was calculated that there are about 300,000 receptor sites per cell either using perfusion experiments at 4 degrees C or isolated hepatocytes.