Potential metabolic mutagens of caffeine and various methylxanthines.

Xanthine N-carbinols, potential metabolites of caffeine and other methylxanthines, have been synthesized, characterized, and derivatized. Such intermediates, the initial metabolites arising from the cytochrome P-450 oxidation of the nitrogen-bound methyl groups, may be viewed as biological N-carbinols capable of alkylating proteins and nucleic acids. Evaluation of these compounds against Salmonella typhimurium, strain TA100, has demonstrated that, in contrast to caffeine, 7-hydroxymethyltheophylline and the 3,7-bis(hydroxymethyl)-1-methylxanthine mixture did exhibit cytotoxicity. There was no evidence of mutagenesis and it is possible that the Ames assay system is not applicable to N-carbinols.

Immune responsiveness of monkeys exposed chronically to cigarette smoke.

Eleven adult male stumptailed monkeys (Macaca arctoides) were chronically exposed to either a low dose (human equivalent of 1 pack/day) or a high dose (human equivalent of 3 packs/day) of high-tar, high-nicotine University of Kentucky reference cigarette smoke for 4-8 years. Several parameters of their immunological response were compared to six nonsmoked control animals. The results from these experiments suggest that cigarette smoking does not significantly affect the response of spleen cells to the mitogens phytohemagglutinin or lipopolysaccharide. However, spleen cells from animals subjected to the heavy dose of cigarette smoke demonstrated a significant reduction in their natural killer cell-mediated lytic activity and a decreased response to concanavalin A. These results suggest that cigarette smoking may have a differential effect on lymphocyte subpopulations, and that the effects on the immune response are related to the dose of cigarette smoke.

Increasing lipid peroxidation by vitamin E deficiency does not augment adriamycin-induced inhibition of hepatic drug metabolism.

Adriamycin treatment in vivo or addition to incubation mixtures in vitro inhibits hepatic drug metabolism. It has been suggested that adriamycin-induced membrane lipid peroxidation may be a mechanism responsible for this activity in vitro. To determine if similar mechanisms operate in vivo, adriamycin inhibition of drug metabolism was compared in rats whose tissue lipid peroxidizability was altered by manipulating dietary levels of vitamin E. Weanling rats maintained on vitamin E deficient (0 ppm) or supplemented (10 or 100 ppm) diets for 12 weeks were given either adriamycin, 5 mg/kg/week, or equal volumes of the saline vehicle for 3 weeks intraperitoneally. Vitamin E deficiency alone (0 ppm, saline pretreatment) produced a 37% increase in hepatic lipid peroxidation without any appreciable alteration in hepatic aniline hydroxylase, ethylmorphine N-demethylase or aryl hydrocarbon hydroxylase activities. Adriamycin pretreatment altered hepatic lipid peroxidizability over corresponding saline pretreated controls dependent on dietary vitamin E. No increase was seen in the 100 ppm group, while 44% and 500% increases occurred at 10 and 0 ppm vitamin E, respectively. Adriamycin pretreatment decreased drug-metabolizing enzyme activity by an average of 32% for aniline hydroxylase, 26% for ethylmorphine N-demethylase and 63% for aryl hydrocarbon hydroxylase. Statistically, decreases in drug metabolism were independent of dietary vitamin E and did not correlate with lipid peroxidizability. These data would suggest that in vivo adriamycin-induced depression of hepatic drug-metabolizing enzymes is not mediated by elevated lipid peroxidation.

Recombinogenic activity of fresh cigarette smoke in Saccharomyces cerevisiae.

A procedure for determining the effect of fresh cigarette smoke on gene conversion in yeast. Saccharomyces cerevisiae D7, is described. Cigarette smoke, generated by a 2-sec, 40-ml puff, once per minute, was puffed into an open-end tube. The smoke was drawn through an exposure vessel containing a continuously stirred, stationary-phase yeast cell suspension, 1-58 sec after generation. Frequency of gene conversion was estimated in samples taken at intervals after the start of exposure. Under these conditions, a five-fold increase in mitotic gene conversion in yeast strain D7 was obtained from exposure to 20 puffs of fresh whole smoke from University of Kentucky Reference Cigarettes (2R1), to 75 puffs from the gas phase of these cigarettes, and to 45 puffs from an acetate filter version (2R1F). Selective removal of genetically active components by acetate filters is suggested since the reduction in recombinogenic activity (55%) is greater than the reduction in total particulate matter yield (25%) of the cigarette. The results indicate that 1) the procedure provides a practical bioassay for determining the effects of fresh smoke on gene conversion in yeast, without external metabolic activation; 2) the gas phase of smoke has recombinogenic activity; and 3) standard acetate filters may selectively remove genetically active components of cigarette smoke.

Influence of dietary selenium on the hepatic and pulmonary enzymes in polychlorobiphenyls-treated rats.

One-month-old male Sprague-Dawley rats maintained for 19 weeks on a low selenium diet with or without supplementation of 2.0 ppm selenium were injected intraperitoneally with either 500 mg PCB (Aroclor 1254)/kg body weight or placebo 5 days prior to sacrifice. In addition to aryl hydrocarbon hydroxylase (AHH) activity, PCB treatment also caused a significant increase in hepatic levels of thiobarbituric acid reactants (TBAR), reduced glutathione (GSH), GSH-peroxidase, GSH reductase, glucose-6-phosphate dehydrogenase (G-6-PD), and GSH-S-transferase in rats on the low selenium diet. The non-selenium-dependent form of GSH peroxidase was mainly responsible for the increase of hepatic GSH peroxidase upon PCB treatment. Only the activities of AHH, GSH-S-transferase, and G-6-PD were significantly higher in the liver of PCB-treated rats fed the selenium-supplemented diet. In contrast, except for AHH activity, the lung GSH and related enzymes were not significantly affected by PCB in either of the two dietary groups. The results suggest that dietary selenium deprivation renders the livers of rats more sensitive to PCB effects.

Increased level of L-ascorbic acid in the plasma of poly-chlorobiphenyls-treated rats and its inhibition by dietary vitamin E.

One-month-old male rats were fed a basal vitamin E deficient diet with or without 100 ppm vitamin E supplementation for 11 weeks and were injected intraperitoneally with either 500mg/kg body weight of polychlorobiphenyls (PCB) in sesame oil or equivalent amount of sesame oil. Five days after PCB treatment, the level of total L-ascorbic acid in the plasma of vitamin E deficient rats increased 69% (p less than 0.001) as compared with 26% (p less than 0.01) of the supplemented group. The dehydro form of ascorbic acid increased 111% (p less than 0.001) and 33% (p less than 0.01), respectively, in the plasma of PCB treated rats maintained on the vitamin E deficient and supplemented diets. The levels of reduced ascorbic acid and of vitamin E in plasma were not significantly altered by PCB in both groups of animals. The results suggest that dietary vitamin E may modify cellular susceptibility to PCB toxicity.