There is available evidence supporting a positive association between alcohol intake and risk of breast cancer. However, there is limited information regarding possible mechanisms for this effect. Past studies from our laboratory suggest that acetaldehyde accumulation in mammary tissue after alcohol intake may be of particular relevance and that cytosolic and microsomal in situ bioactivation of ethanol to acetaldehyde and free radicals and the resulting stimulation of oxidative stress could be a significant early event related to tumor promotion. In the present studies repetitive alcohol drinking for 28 days was found to produce significant decreases in the mammary tissue content of GSH and alpha tocopherol and in glutathione S-transferase or glutathione reductase activities. In contrast, glutathione peroxidase activity was slightly increased. Malondialdehyde determinations did not show the occurrence of lipid peroxidation while the xylenol orange procedure gave positive results. The mammary microsomal metabolism of ethanol to acetaldehyde was not induced after an acute dose of ethanol or acetone able to induce the activity of its liver counterpart. The cytosolic pathway of alcohol metabolism instead was significantly enhanced by these two treatments. No increased generation of comet images was found either in mammary tissue or in liver under the experimental conditions tested. Results suggest that, while acetaldehyde accumulation in mammary tissue could be a critical event resulting from increasing production of acetaldehyde in situ plus an additional amount of it arriving via blood, other factors such as poor handling of the accumulated acetaldehyde could be also relevant.

It is known that drinking alcohol can lead to reproductive problems in women. In this study, we analyzed the possibility that part of those effects were mediated through alterations of ovarian function related to ethanol oxidation to acetaldehyde occurring in situ. Biotransformation in the rat ovary cytosolic fraction was partially inhibited by allopurinol, suggesting the participation of xanthine oxidoreductase in the process. Microsomal pathway was of enzymatic nature, requiring nicotinamide adenine dinucleotide phosphate-oxidase (NADPH), sensitive to oxygen and significantly inhibited by sodium diethyldithiocarbamate, 4-methylpyrazole and diphenyleneiodonium. Aldehyde dehydrogenase activity was detected by histochemistry in the ovarian tissue, in the strome surrounding the follicle while no alcohol dehydrogenase was detected. However, biochemical determination of alcohol dehydrogenase and aldehyde dehydrogenase activities in rat ovarian tissue revealed the presence of some activity of both enzymes but significantly lower than those found in the liver. By repetitive exposure of animals to ethanol, the microsomal metabolism to acetaldehyde was increased but not in the case of the cytosolic fraction. In these animals, t-butylhydroperoxyde-promoted chemiluminiscence was increased in comparison to control, revealing an increased susceptibility to oxidative stress due to alcohol drinking. Ultrastructure of ovarian tissue from rats exposed chronically to alcohol revealed alterations at the level of the granulosa; theca interna and pellucida zones. In the secondary follicle, alterations consisted of marked condensation of chromatin attached to the nuclear inner membrane. Intense dilatation of the outer perinuclear space could be observed. There was a marked dilatation of the rough endoplasmic reticulum accompanied of significant detachment of ribosomes from their membranes. Mitochondria appeared swollen. In the zona pellucida, most of the cell processes from oocyte and corona radiata cells were absent or broken totally or in part. Results suggest that in the rat ovary, metabolism of ethanol to acetaldehyde may play a role in alcohol effects on female reproductive function.

Controversial studies from others suggested that alcohol intake could be associated with some deleterious effects in the uterus. Not all the effects of alcohol drinking on female reproductive organs can be explained in terms of endocrine disturbances. Deleterious effect of alcohol or its metabolites in situ could also play a role. Accordingly, we found a metabolism of alcohol to acetaldehyde in the rat uterine horn tissue cytosolic fraction mediated by xanthine oxidoreductase, requiring a purine cosubstrate and inhibited by allopurinol. This activity was detected by histochemistry in the epithelium and aldehyde dehydrogenase activity was detected in the muscular layer and in the serosa. There was a microsomal process, not requiring NADPH and of enzymatic nature, oxygen-dependent and inhibited by diethyldithiocarbamate, diphenyleneiodonium and partially sensitive to esculetin and nordihydroguaiaretic acid. The presence of metabolic pathways in the uterine horn able to generate acetaldehyde, accompanied by a low capacity to destroy it through aldehyde dehydrogenase, led to acetaldehyde accumulation in the uterus during ethanol exposure. Results suggest that any acetaldehyde produced in situ or arriving to the uterine horn via blood would remain in this organ sufficiently to have the opportunity to react with critical molecules to cause deleterious effects.

Two nitroheterocyclic drugs, nifurtimox (NFX) and benznidazole (BZ), used in the treatment of Chagas’ disease have serious side effects attributed to their nitroreduction to reactive metabolites. Here, we report that these drugs reach the mammary tissue and there they could undergo in situ bioactivation. Both were detected in mammary tissue from female Sprague-Dawley rats after their intragastric administration. Only NFX was biotransformed by pure xanthine-oxidoreductase and from tissue cytosol. These activities were purine dependent and were inhibited by allopurinol. Also, only NFX was biotransformed by microsomes in the presence of β-nicotinamide adenine dinucleotide phosphate, reduced form (NADPH), and was inhibited by carbon monoxide and partially by diphenyleneiodonium. NFX treatment produced significant decrease in protein sulfhydryl content after 1, 3 and 6 hours; no increases in protein carbonyl content at any time tested and significantly higher levels of lipid hydroperoxides at 3 and 6 hours; besides, ultrastructural observations after 24 hours showed significant differences in epithelial cells compared to control. These findings indicate that NFX might be more deleterious to mammary tissue than BZ and could correlate with early reports on its ability to promote rat mammary tissue toxicity.

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