Rat breast microsomal biotransformation of ethanol to acetaldehyde but not to free radicals: Its potential role in the association between alcohol drinking and breast tumor promotion

We recently showed that mammary cytosolic xanthineoxidoreductase had the ability to bioactivate ethanol (EtOH) to acetaldehyde (AC) and free radicals. In thepresent study, we report that the microsomal fraction also biotransforms EtOH to AC. One pathway requires NADPH and the others do not. Both need oxygen. TheNADPH-dependent pathway is not inhibited by CO:O(2) (80:20) or SKF 525A and that excludes the participation of cytochrome P450. It is inhibited bydiethyldithiocarbamate (DDTC), sodium azide, and diphenyleneiodonium (DPI) butnot by desferrioxamine, which suggests a possible role of a non-ironcopper-requiring flavoenzyme. The process was partially inhibited bythiobenzamide (TBA), methylmercaptoimidazole (MMI), and nordihydroguaiaretic acid(NDG) but not by dapsone, aminotriazole, or indomethacin. These results suggestthe potential participation of flavine monooxygenase and of lipooxygenase or ofperoxidases/oxidases having similar characteristics but not of lactoperoxidase orcyclooxygenase. The pathway not requiring NADPH could also be partially inhibitedby DDTC, NDG, azide, DPI, and TBA or MMI but not by the other chemicals. Littleactivity proceeds under nitrogen. Oxidases or peroxidases might be involved. Noformation of 1-hydroxyethyl radicals was detected either in the presence orabsence of NADPH. The nature of the EtOH bioactivating enzymes involved remainsto be established. However, the fact remains that an activation of EtOH to AC wasfound in mammary tissue and could have a significant effect in some stages of theprocess of breast tumor promotion by EtOH.Fil: Castro, Gerardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Delgado de Layño, Aurora M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Costantini, Martin Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Castro, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentin

Rat ventral prostate microsomal biotransformation of ethanol to acetaldehyde and 1-hydroxyethyl radicals: Its potential contribution to prostate tumor promotion

Rat ventral prostate microsomal fraction was able to biotransform ethanol to acetaldehyde and 1-hydroxyethyl radicals (1HEt) in the presence of NADPH and oxygen. The enzymatic processes involved were not inhibited by desferrioxamine, CO, SKF 525A, 4-methylpyrazole, or polyclonal antibody against P450 reductase but they were significantly inhibited by diethyldithiocarbamate, 2-mercapto-1-methylimidazol, thiobenzamide, or diphenyleneiodonium chloride. Results would suggest the partial participation in these ethanol bioactivation processes of flavin containing monooxygenase (FMO) and/or other flavin dependent oxidases/ peroxidases and of a non-iron metal-containing enzymes. Acetaldehyde and free radicals production by prostate microsomal fraction might potentially contribute to tumor promotion in heavy alcohol drinkers.Fil: Castro, Gerardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Delgado De Layño, Aurora, M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Costantini, Martin Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Castro, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentin

Rat liver microsomal and nuclear activation of methanol to hydroxymethyl free radicals

Recent studies from other laboratories reported that during methanol intoxication lipid peroxidation and protein oxidation in liver occurred. Further, they detected free radicals-PBN adducts in bile and urine of methanol poisoned rats. In this work, we report the presence in liver microsomes and nuclei of NADPH dependent processes of hydroxymethyl (HMet) radical formation. The detection of HMet radicals was performed by GC/MS of the trimethylsilyl derivatives of the PBN (N-tert-butyl-a-phenylnitrone)-radical adducts. The formation of HMet radicals was observed only under nitrogen, in these in vitro conditions. Formation of formaldehyde from methanol was observed in aerobic incubation mixtures containing either microsomes or nuclei but also under nitrogen using microsomes. The latter process was not inhibited by diphenyleneiodonium while the anaerobic microsomal one producing HMet was strongly inhibited by it. This shows that they are independent processes. Results suggest that both, liver nuclei and microsomes are able to generate free radicals during NADPH-mediated methanol biotransformation.Fil: Castro, Gerardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Costantini, Martin Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Delgado De Layño, Aurora, M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Castro, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentin