ENZYMATIC RESPONSES OF DROSOPHILA-MELANOGASTER TO LONG-TERM AND SHORT-TERM EXPOSURES TO ETHANOL

The effects of environmental ethanol on larva-to-pupa survival and on the activities of four enzymes were investigated in three drosophila m elanogaster strains. The strains had different allelic combinations at the Odh and Aldox loci on their third chromosomes, but they all carri ed the Adh(S)-Gpdh(F) allelic combination on the second chromosome. Re plicates of each of the strains were exposed to three different ethano l treatments: (i) no ethanol in the medium (control); (ii) 5% ethanol for a single generation (short-term exposure); (iii) 5% ethanol for 20 generations (long-term exposure). In all experiments, the activities of four enzymes (ADH, ODH, GPDH and AOX) were measured in larvae, pupa e and adults. The results showed that (i) the larval and adult metabol ic responses to environmental ethanol were different; (ii) enzyme acti vity changes under short-term exposure differed from those measured un der long-term exposure; (iii) the activities of the allozymes common t o all strains (ADH-S and GPDH-F), differed depending on the genetic ba ckground. Changes in larva-to-pupa survival were seen when the larvae of control and exposed lines of the three strains were confronted with various concentrations of ethanol. In all three strains, the exposed lines had significantly higher initial survival rate and ethanol toler ance than the control lines. Strain-specific differences were observed in the ethanol tolerance of both types of line.