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
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
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Fig. 1. Salicylate levels in the haemolymph of third instar larvae fed on a
salicylate-enriched diet. (A) Levels of salicylate in the haemolymph of larvae
fed on a 20 mmol l–1 salicylate-enriched diet for different
periods. (B) Levels of salicylate in the haemolymph of larvae fed for 24 h on
diets with different concentrations of salicylate. Each point represents the
mean ± s.e.m. of 25–50 samples. The curve was fitted to the
Michaelis–Menten equation by non-linear regression analysis.
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Fig. 2. Kinetics of salicylate elimination from the haemolymph of third instar
D. melanogaster larvae. Haemolymph salicylate concentration was
measured (0–6 h) after transfer of larvae that had been fed for 24 h on
a 20 mmol l–1 salicylate-enriched diet to a salicylate-free
diet. Solid and broken lines indicate the control and experimental group,
respectively. Experimental larvae were raised for 10 days on a 10 mmol
l–1 salicylate-enriched diet and subsequently transferred for
15 h to a salicylate-free diet, whereas control larvae were raised on a
salicylate-free diet (inset). Each point represents the mean (± s.e.m.)
of 25–50 samples. The curve was fitted to a one-compartment model by
non-linear regression analysis.
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Fig. 3. Effects of chronic exposure of D. melanogaster larvae to dietary
salicylate on (A) fluid secretion rate, (B) salicylate concentration in the
secreted fluid and (C) transepithelial flux of salicylate across the main
segment of isolated Malpighian tubules set up in the Ramsay assay. Each point
represents the mean ± s.e.m. of 7–10 tubules. Solid and broken
lines indicate the control and experimental group, respectively. Experimental
larvae were raised for 10 days on a 10 mmol l–1
salicylate-enriched diet. Control larvae were raised on a salicylate-free
diet.
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Fig. 4. Effects of Na+-free bathing saline on (A) fluid secretion rate
and (B) transepithelial flux of salicylate across the main segment of isolated
Malpighian tubules set up in the Ramsay assay. Malpighian tubules were bathed
in control saline (solid bars) or Na+-free saline (hatched bars)
containing 50 µmol l–1 salicylate. Experimental larvae
were raised for 10 days on a 10 mmol l–1 salicylate-enriched
diet. Control larvae were raised on a salicylate-free diet. Secreted fluid
droplets were collected after 40 min. Values are means ± s.e.m.
(N=6–9 tubules). Asterisks indicate significant differences
between control and experimental groups (*P<0.05,
**P<0.01; t-test, N=6–8).
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Fig. 5. Effects of 1 mmol l–1 cAMP on the rate of fluid secretion
by the main segment of isolated Malpighian tubules set up in the Ramsay assay.
The first secreted droplet was collected at 30 min (solid bars) and the second
secreted droplet (hatched bars) was collected 30 min after adding cAMP.
Experimental larvae were raised for 10 days on a 10 mmol l–1
salicylate-enriched diet. Control larvae were raised on a salicylate-free
diet. Values are means ± s.e.m. (N=8–10 tubules).
Asterisks indicate significant differences in fluid secretion rate before and
after adding cAMP (**P<0.01,
***P<0.001; paired t-test,
N=8–10).
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Fig. 6. Effects of 10 µmol l–1 leucokinin I on the rate of
fluid secretion by the main segment of isolated Malpighian tubules set up in
the Ramsay assay. The first secreted droplet was collected at 30 min (solid
bars) and the second secreted droplet (hatched bars) was collected 30 min
after adding leucokinin I. Experimental larvae were raised for 10 days on a 10
mmol l–1 salicylate-enriched diet. Control larvae were raised
on a salicylate-free diet. Values are means ± s.e.m.
(N=7–9 tubules). Asterisks indicate significant differences in
fluid secretion rate before and after adding leucokinin are indicated
(***P<0.001; paired t-test,
N=7–9).
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Fig. 7. Effects of chronic exposure of D. melanogaster larvae to dietary
salicylate on salicylate influx across three segments of the isolated gut.
Fluxes were measured using the scanning ion electrode technique as described
in the Materials and methods. Gut segments were bathed in 30 mmol
l–1 Cl– saline containing 100 µmol
l–1 salicylate. Flux for each segment of each larva was
calculated as the mean value for three sites separated by 480 µm for the
midgut and 200 µm for the ileum and rectum. Solid and hatched bars indicate
mean ± s.e.m. for 4–5 larvae in the control and experimental
group, respectively. Experimental larvae were raised for 10 days on a 10 mmol
l–1 salicylate-enriched diet. Control larvae were raised on a
salicylate-free diet. No significant differences between groups were observed
(P>0.05).
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© The Company of Biologists Ltd 2007
