EFFECTS OF DIETARY ETHANOL, ACETALDEHYDE, 2-PROPANOL AND ACETONE ON THE VARIATION OF SEVERAL ENZYME-ACTIVITIES INVOLVED IN ALCOHOL METABOLISM OF DROSOPHILA-MELANOGASTER ADULTS

The role of ethanol, 2-propanol and their respective in vivo oxidized derivatives (acetaldehyde and acetone) in the modulation of several enzyme activities (ALDH, ALDH(ADH), ADH(OX), ADH(r) and AKR) involved in the metabolism of alcohols has been studied in Drosophila melanogaster adults. Flies from a wild (LRC-S) and an ADH-null (bAdh(n4)) strain were fed diets containing each mentioned compound and the temporal variation in both mortalities and enzyme activities were determined. In addition, in vitro and in vivo inhibitions of the enzyme activities were studied in order to determine the specificity of the activities assayed. Although ADH+ flies are able to tolerate all the four compounds better than ADH- ones, in wild flies none of the activities assayed were subject to modulation by dietary ethanol, acetaldehyde, 2-propanol or acetone. 2-Propanol and acetone reduced the ADH dependent activities but this was associated with a post-translational process: the formation of the inhibitory ADH:NAD:acetone complex. In ADH-flies, an intriguing result was obtained: dietary 2-propanol and acetone were observed to induce ALDH enzyme activity. However, this induction must be taken with precautions. We also report that 2-propanol is relatively more toxic than acetone in D. melanogaster adults. In conclusion, our results support that, to the contrary of what occurs in larvae, the short-term modulation of the enzyme activities involved in the metabolism of alcohols, does not appear to be a major mechanism used by D. melanogaster adults to respond to the presence of such compounds in the medium. Their ability to move to non-toxic feeding sites seems to be successful enough to avoid the toxic effect of alcohols.