Collagen biosynthesis enzymes in serum and hepatic tissue in liver disease

Abstract. Serum immunoreactive prolyl hydroxylase protein was measured in sixty-five patients with liver disease, and liver prolyl hydroxylase activity, immunoreactive prolyl hydroxylase protein and collagen hydroxyproline in forty of these patients. Serum immunoreactive prolyl hydroxylase protein was above the 95% confidence limit of the controls in most patients with primary biliary cirrhosis, portal cirrhosis, acute hepatitis and cancer with liver metastases, but below this in most patients with fatty liver, chronic active hepatitis, extrahepatic cholestasis, cholangitis, cancer without liver metastases and other malignant diseases. Elevated serum immunoreactive prolyl hydroxylase protein decreased rapidly with time in acute hepatitis but not in primary biliary cirrhosis. Liver prolyl hydroxylase activity and immunoreactive prolyl hydroxylase protein were elevated in the same diseases as serum immunoreactive prolyl hydroxylase protein, and correlated significantly with the latter whereas no correlation was found between serum immunoreactive prolyl hydroxylase protein and collagen hydroxyproline. Serum immunoreactive prolyl hydroxylase protein correlated highly significantly with serum alkaline phosphatase and weakly with serum aspartate aminotransferase in primary biliary cirrhosis, but not in any other disease. No correlation was found between serum immunoreactive prolyl hydroxylase protein and other tests of liver function. The results suggest that changes in serum immunoreactive prolyl hydroxylase protein in liver disease primarily reflect changes in this enzyme in the hepatic tissue, and that assays of serum immunoreactive prolyl hydroxylase in liver disease may give useful information on the actual hepatic collagen synthesis.