Effect of repeated ether anesthesias on the mono-oxygenase system of rat liver S-9 fraction

This study was designed to investigate the effect of ether anesthesia in rats, before i.p. injections to induce the mono-oxygenase enzyme system, on biochemical properties of liver S9 fractions. Aminopyrine N-demethylase and rho-nitroanisole O-demethylase activity levels, their stability, and lipid peroxidation were determined in S9 fractions after etherization (about 1 min in ether vapor chamber daily for 3 consecutive days, before i.p. injections of Na-phenobarbital and beta-naphthoflavone) and compared with controls receiving the same injections without etherization. The activities were slightly (but not significatively) enhanced after this treatment, but stability was markedly and significatively greater after 1 h of incubation in the conditions of the liver microsomal assay (+ 14.8% and + 74.7%, respectively); lipid peroxidation was strongly and significatively depressed (-76.0%). Etherization sufficient to kill the animals on the 4th day resulted in equally active but less stable S9 fraction enzymes. Dimethylnitrosamine (as a standard premutagen) was assayed with the D7 strain of Saccharomyces cerevisiae using S9 fractions obtained from both anesthetized and nonanesthetized rats. According to biochemical data, results obtained with S9 from partially anesthetized rats were comparable with the conventional ones (S9 from nonanesthetized rats). On the contrary, the use of more prolonged ether anesthesia, including one on the day the animals are killed, gives S9 fraction significantly less effective. We conclude that if brief etherizations are used, for i.p. injections only, the S9 fractions obtained are entirely satisfactory and the procedures involved in production are simplified; the additional animal treatment (etherization) must be specified.