Isozyme shift in cultured fetal human hepatocytes: a study of pyruvate kinase and phosphofructokinase

Hepatocytes from a 4-month old fetus were cultured for 15 days. We found that fetal hepatocytes contained some R₁ (precursor) form of L-type pyruvate kinase. Culture was associated with a considerable increase of the M₂-type pyruvate kinase activity, but some L-type enzyme could be detected even after 10 days.Isozyme shift of phosphofructokinase seemed to be a progressive rather low phenomenon. Fetal hepatocytes showed an increase of the F-type form and a disappearance of the M-type form during culture. However, by day 10, the L-type enzyme remained predominant; this is in striking contrast with the findings reported on cultured fibroblasts.From these results, pyruvate kinase can be considered as a “strong” marker of cell differentiation, while phosphofructokinase is rather a “weak” marker.