[Effect of phorbol ester on protein kinase C and tyrosine protein kinase in human hepatocarcinoma cell line].

Phorbol-12-myristate-13-acetate (PMA) induced a dose-dependent proliferation of human hepatocarcinoma cell line SMMC-7721. In the presence of 100 nmol/L PMA, the activity of alkaline phosphatase was decreased and gamma-glutamyltransferase increased in the cell, suggesting that PMA is a proliferative inducer of hepatocarcinoma cell. PMA (100 nmol/L) also lead to a cytosol to membrane translocation of protein kinase C (PKC) within 5 minutes and down regulation after 1 hour. The decline of PKC activity in cytosolic fraction was far faster than that of membranous fraction. After long-term treatment with PMA for 1-5 days, the activities of PKC in cytosolic or membranous fraction almost disappeared, but the tyrosine protein kinase in both subcellular fractions was increased, being most obviously on the third day of culture. The increase in cytosolic TPK was more than that of membranous TPK, further indicating that TPK is a marker of cell proliferation.