EFFECT OF 12-O-TETRADECANOYLPHORBOL 13-ACETATE ON DNA SYNTHESIS IN PROLIFERATING RAT HEPATOCYTES IN PRIMARY CULTURE

Abstract

DNA synthesis in primary culture of rat hepatocytes was initiated over 16h after the beginning of culture and reached a peak between 32h and 40h under the conditions of this study. The addition of 12-O-tetradecanoylphorbol 13-acetate (TPA) (100 ng/ml) during the initial 24h of culture inhibited DNA synthesis, while addition between 16h or 20h and 24h stimulated DNA synthesis. Chelator-extractable and calcium-dependent protein kinase activity in the soluble fraction of hepatocytes with TPA addition during the initial 24h of culture was apparently reduced at 8, 12, 16 and 24h. It is suggested that TPA addition just prior to the initiation of DNA synthesis activates proten kinase C (PKC) and stimulates DNA synthesis, whereas TPA addition at an early stage of culture inhibits DNA synthesis, possibly because of PKC depletion.