Intracellular enzymes of collagen biosynthesis in rat liver as a function of age and in hepatic injury induced by dimethylnitrosamine. Changes in prolyl hydroxylase, lysyl hydroxylase, collagen galactosyltransferase and collagen glucosyltransferase activities.

The relationship between the changes in the four enzyme activities catalysing intracellular post-translational modifications in collagen biosynthesis were studied in rat liver as a function of age and in experimental hepatic injury induced by the administration of dimethylnitrosamine. During aging, relatively large changes were found in prolyl hydroxylase and lysyl hydroxylase activities, whereas only minor changes took place in collagen galactosyltransferase and collagen glucosyltransferase activities. In hepatic injury, the two hydroxylase activities increased earlier and to a larger extent than did the two glycosyltransferase activities, and the largest was found in lysyl hydroxylase activity. The data support previous suggestions that changes in the rate of collagen biosynthesis in the liver cannot be explained simply by a change in the number of collagen-producing cells, but regulation of the enzyme activities existed, so that the two hydroxylase activities altered considerably more than did the two collagen glycosyltransferase activities.