Tetrachloroethane, pentachloroethane, and hexachloroethane: genetic and biochemical studies

Effect of magnetic fields on rodent monooxygenase enzymes

The effects of 50 Hz, 1.2 mT magnetic fields (MFs) were tested on hepatic monooxygenase enzymes of basal and beta-naphthoflavone-phenobarbital-preinduced rats and mice. An inductive effect on cytochrome P-450 level and on some enzymatic cytochrome P-450-dependent activities was observed in basal mice after MF exposure. Enzymatic activities in preinduced mice and rats were reduced by MFs, the degree of reduction depending on the enzyme. A specific inhibitory effect was determined in some of the assayed activities and in the relative peculiar P-450 isoforms detected by Western blot analysis.

Metabolism of 5-methoxypsoralen by Saccharomyces cerevisiae

Incubation of methoxypsoralen (5-MOP) in the presence of diploid yeast cells (Saccharomyces cerevisiae) before UV-A exposure leads to an incubation-time dependent decrease of photoinduced genotoxic effects. The reduction in photoinduced genotoxicity is stronger in cells grown in the presence of 20% glucose and containing high levels of cytochrome P-450 than in cells grown in the presence of 0.5% glucose and containing undetectable levels of cytochrome P-450. Inhibition of P-450 activity by specific inhibitors, such as tetrahydrofuran and metyrapone, strongly affects the observed decrease in 5-MOP genotoxicity, indicating the involvement of P-450 in 5-MOP metabolism. As demonstrated by spectrophotometric and chromatographic (HPLC) analysis during incubation of 5-MOP with P-450 containing yeast cells, 5-MOP gradually disappears from the cell supernatant of the incubation mixture. The reduction in the chromatographic peak corresponding to 5-MOP is accompanied by the appearance of a new peak that probably corresponds to a metabolite. As shown by the use of P-450 specific inhibitors, the metabolite appears to be due to P-450 mediated 5-MOP metabolisation. Its UV absorption spectrum suggests an alteration of the pyrone moiety of the 5-MOP molecule.