INFLUENCE OF COLLAGEN GEL SUBSTRATA ON CERTAIN BIOCHEMICAL ACTIVITIESOF HEPATOCYTES IN PRIMARY CULTURE

In order to study the influence of cell shape as modulated by the extr acellular matrix on the cellular activity, hepatocytes isolated from l iver were maintained on collagen I coated plastic substrata and collag en I gel substrata and certain hepatocyte specific functions were inve stigated. The incorporation of (3)[H]-leucine into total proteins and albumin secreted by cells maintained on collagen gel was found to be s ignificantly higher compared to those maintained on a collagen coated plastic substrata, indicating that hepatocytes on collagen gel have an enhanced albumin synthesizing capacity. Increased incorporation of (3 5)[S]-sulphate into total proteoglycans (PG) and a relatively higher f raction of the (35)[S]-PG in the extracellular space showed an increas ed rate of synthesis and secretion of sulphated PGs by cells maintaine d on collagen gels. But in contrast to the above results, the incorpor ation of (3)[H]-leucine into cytokeratins C-8, C-18 and actin were sig nificantly low in cells maintained on collagen gel. The tyrosine amino transferase activity exhibited by hepatocytes preincubated with dexam ethasone on collagen gel was also significantly low. The different for ms of collagen substrata appeared to have no effect on the amino acid transport by hepatocytes, further suggesting that the various hepatocy te specific functions are not uniformly altered when hepatocytes are m aintained on three-dimensional collagen gel substrata. These results i ndicate that the shape of the cell as determined by the nature of the matrix substratum influences the synthetic activity of secretory prote ins and those remaining intracellularly, differently.