Regulation of alcohol dehydrogenase in Drosophila melanogaster by dietary alcohol and carbohydrate

Abstract

When fed to Drosphila melanogaster Canton-S wild-type larvae cultured axenically on Sang's modified medium C with 0.5% (w/v) sucrose, 2.5% (v/v) ethanol induced an alcohol dehydrogenase (ADH) activity at least 2.5-fold higher than the activity in larvae fed an unsupplemented 0.5% sucrose diet. Ethanol induced only a 2-fold change in ADH cross reacting material (CRM), suggesting that there was also a post-translational modification of ADH. The addition of dietary sucrose to the diet (at 5%, w/v) exerted similar, but lesser effects on ADH activity and CRM. Increasing dietary sucrose to 5% in the presence of 2.5% ethanol decreased ADH activity and CRM to levels below those attained in the 0.5% sucrose-2.5% ethanol diet. Upon examination, dietary ethanol was found to decrease the relative concentration of ADH-1 and increase the concentrations of ADH-3 and ADH-5 in larvae; sucrose had a similar but lesser effect on the isozyme pattern. Because dietary ethanol increased both the total NAD content and the NADH NAD + ratio, the diet-induced changes in isozyme pattern were proposed to be linked to the relative amounts of NADH, NAD + and ADH enzyme in larval tissues. Larval ADH activity is modulated by both dietary alcohol and carbohydrate.