Caffeine metabolism in <i>Drosophila melanogaster</i> and the influence of cytochrome P450 inhibitor.

<p>A- Separation of non-radiolabeled standards of caffeine and metabolites (lane 1) with a homogenate of wild-type four-days-old <i>Drosophila</i> male flies (w¹¹¹⁸) exposed with radiolabeled caffeine for 2 hours (lane 2) on thin layer chromatography. B- The total amount of caffeine derived metabolites was strongly decreased in the body of male flies after exposure to caffeine mixed with metyrapone (+), as compared to control food (-). The amounts were evaluated by densitometry which is based on the comparison of the areas under the curve (AUC) for both metabolites and caffeine. Bars indicate the mean values (±s.e.m.). Significant differences are indicated by asterisks (Student’s t-test *** p < 0.001; n = 3). C- Interspecific variation for the level of major caffeine metabolites. The proportions of theobromine, paraxanthine and theophylline and of the unidentified M2 metabolite detected in fly bodies after caffeine exposure (18mM) are indicated as the mean (±s.e.m.; n = 4). In <i>Drosophila melanogaster</i>, these amounts were evaluated by measuring the relative intensity of the radiolabelled signal associated with each metabolite after thin layer chromatography separation. The proportion of these compounds detected in <i>Drosophila melanogaster</i> was compared with that reported for <i>Rattus norvegicus</i> and <i>Homo sapiens</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117328#pone.0117328.ref025" target="_blank">25</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117328#pone.0117328.ref028" target="_blank">28</a>].