Procollagen production by rat hepatocytes in primary culture

Hepatocytes were obtained from rat liver and maintained in primary culture for periods up to 14 days. Collagen synthesis was maximal after 3-5 days and declined thereafter. The rate of collagen production was approx. one-tenth that observed by rat skin fibroblasts of the same animals after 3-5 passages. Type I procollagen, the major macromolecular collagenous species, was identified as a 450 000 dalton molecule which was converted to 120 000 dalton, denatured, reduced procollagen chains. Prior pepsin digestion of the native procollagen released 95 000 dalton collagen chains identified as alpha 1(I) and alpha2(I) by co-migration with carrier rat skin type I collagen chains. The production of type III procollagen was also tentatively identified by DEAE-cellulose chromatography. This material was isolated and identified with type-specific antibodies developed against the amino-terminal extension peptide of bovine skin type III procollagen. The relative distribution of type I:type III procollagen was estimated at 7:3 similar to the ratio previously found in whole rat liver. No evidence of type IV or type V procollagen biosynthesis was observed. These results suggest that rat hepatocytes in primary culture are capable of interstitial type I and type III collagen biosynthesis in a ratio similar to that found in their parent hepatic tissue in situ. They also suggest that the less abundant type IV (basement membrane-associated) or type V are not major collagenous products of these cells.