Influence of γ-rays on the mouse liver cytochrome P450 system and its modulation by phenothiazine drugs

Purpose: Phenothiazine drugs have been found to sensitize hypoxic cancer cells while offering protection to normal cells. Since phenothiazines are known to induce the cytochrome P450 system, its radiomodulation by phenothiazines has been examined. Materials and methods: Mice were administered phenothiazines intraperitoneally and irradiated with different doses of gamma-rays at 1.38 Gy/min. The activities of NADPH-cytochrome P450 reductase and NADH-cytochrome b(5) reductase, the content of cytochrome P450 and b(5), the extent of lipid peroxidation as well as the activities of LDH, XO, SOD, GST and DTD were determined in the liver. Results: The levels of different components of the cytochrome P450 system and antioxidant enzymes were enhanced up to 5 Gy and decreased thereafter. However, a progressive increase was noticed in peroxidative damage and the activities of LDH and XO. Administration of phenothiazines enhanced the radiation effect on components of the cytochrome P450 system (except NADH-cytochrome b(5) reductase) and the activities of SOD, GST and DTD. Concomitantly, phenothiazines inhibited lipid peroxidation, LDH and XO. Conclusions: Activation of the cytochrome P450 system by phenothiazines leading to the enhancement of antioxidant potential of animals and free-radical scavenging are attributes of the radioprotective action of phenothiazines.