Influence of extracellular proline on collagen synthesis in rat liver slices

The synthesis of collagen was measured in incubated rat liver slices. The concentration of proline in the medium was varied, but the specific radioactivity of proline was kept constant. The synthesis of total protein was found to be about 500-fold that of collagen. The incorporation into hydroxyproline--that is, the synthesis of collagen--and the total incorporation of proline into protein were dependent on the concentration of proline in the medium, by Michaelis-Menten kinetics, with an apparent Km of 0.40 mM for the synthesis of collagen and 0.43 mM for the synthesis of total protein.