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First published online June 29, 2007
Journal of Experimental Biology 210, 2464-2471 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003152
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Effects of chronic exposure to dietary salicylate on elimination and renal excretion of salicylate by Drosophila melanogaster larvae

Esau Ruiz-Sanchez* and Michael J. O'Donnell

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada

* Author for correspondence (e-mail: ruizsae{at}mcmaster.ca)

Accepted 18 April 2007

The effects of chronic exposure to dietary salicylate on elimination and renal excretion of salicylate by D. melanogaster larvae were evaluated using salicylate-selective microelectrodes. Larvae chronically exposed to dietary salicylate showed 25% less salicylate in the haemolymph compared to the control group after feeding on a salicylate-enriched diet. By 1 h after transfer to a salicylate-free diet the levels of salicylate in the haemolymph of larvae raised on dietary salicylate were 46% lower than in the control group. Salicylate flux increased dramatically across Malpighian tubules but not across midgut or hindgut isolated from larvae chronically exposed to dietary salicylate, relative to the control group. Malpighian tubules isolated from experimental larvae showed a 4.7-fold increase in Kt and a nearly 5-fold increase in Jmax relative to the control. These changes in salicylate transport were accompanied by a 3.2-fold increase in fluid secretion rate. Moreover, the high rates of fluid secretion by the Malpighian tubules isolated from experimental larvae were stimulated 2.1-fold and 2.8-fold when tubules were challenged with 1 mmol l–1 cAMP and 10 µmol l–1 leucokinin I, respectively. Taken together, these results indicate that chronic exposure of D. melanogaster larvae to dietary salicylate alters elimination of such toxins from the haemolymph and increases the basal rate of fluid secretion and excretion of salicylate by the Malpighian tubules.

Key words: salicylate, insect renal system, toxin elimination






© The Company of Biologists Ltd 2007