Radiation-induced translocation of protein kinase C through membrane lipid peroxidation in primary cultured rat hepatocytes

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Abstract
A mechanism of radiation-induced activation of protein kinase C was investigated in primary cultured rat hepatocytes. Irradiation of hepatocytes with 5 Gy or 50 Gy of gamma-rays caused an immediate and transient increase in the activity of protein kinase C in the membrane fraction, and a decrease in this activity in the cytosol fraction. A ligand binding procedure for protein kinase C using 3H PDBu demonstrated that PDBu binding content increased in the membrane fraction and decreased in the cytosol fraction following irradiation. These results suggest that protein kinase C molecules were translocated from cytosol to the membrane after irradiation of the hepatocytes. Irradiation also induced lipid peroxidation of hepatocytes in the range from 0 to 50 Gy in a radiation dose-dependent fashion. This induction of lipid peroxidation was markedly suppressed by the addition of Trolox, a radical scavenger. Treatment of hepatocytes with Trolox also caused simultaneous inhibition of the radiation-induced increase in the PDBu binding content of the membrane fraction. We conclude that radiationinduced activation of protein kinase C results from the translocation of protein kinase C from cytosol to membrane due to membrane lipid peroxidation through reactive oxygen species produced by radiation.

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