The uptake of ornithine and lysine by isolated hepatocytes and fibroblasts.

The uptake of ornithine and lysine by isolated hepatocytes and cultured human skin fibroblasts were studied. Both types of cells can accumulate these amino acids via a saturable and a non-saturable process, the latter being active at high substrate concentration. The apparent Km for ornithine and lysine for the saturable process in hepatocytes were 0.26 and 0.94 mM respectively, those values for fibroblasts were found to be 0.43 and 0.57 mM respectively. Fractionation of the cells by the digitonin technique into a cytosolic compartment and a particulate compartment, showed that a rapid equilibration occurs between the external medium and the cytosolic compartment of hepatocytes and fibroblasts.