First published online June 6, 2005
Journal of Experimental Biology 208, 2227-2236 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01617
Specificity of the fluorescein transport process in Malpighian tubules of the cricket Acheta domesticus
Douglas S. G. Neufeld1,*,
Ross Kauffman2 and
Zachary Kurtz1
1 Department of Biology, Eastern Mennonite University, Harrisonburg, VA
22802, USA
2 Ohio State University, School of Public Health, Columbus, OH 43210,
USA
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Fig. 1. Example fluorescence microscopy traces of fluorescein uptake in the
presence and absence of a representative OAT inhibitor, methotrexate. During
an uptake trial, the signal trace shows an initial rapid increase in
fluorescence due to the change-out of chamber with fluid containing FL (a),
followed by a slower increase representing accumulation in the tubule (b).
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Fig. 2. Brightfield (left) and fluorescence (right) micrographs showing FL
accumulation in Acheta Malpighian tubules. In some cases,
fluorescence was stronger in the lumen (A), while in others it was more
generally dispersed through lumen and cell (B). In (C) FL is present in both
the Malpighian tubule (right) and the larger ureter (left) that connects
Malpighian tubules to intestine.
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Fig. 3. Inhibition of FL accumulation by mono- and dicarboxylic acids representing
a range of sizes (as indicated by the number of carbons in the backbone).
Sample sizes range from 3 to 7 tubules, except for `no inhibitor', which
represents all control trials (N=27). *Change in uptake
rate (second measurement period relative to first measurement period) in the
presence of inhibitor significantly different from uptake rate in absence of
inhibitor; P<0.05, paired t-test.
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Fig. 4. Inhibition of FL accumulation by glutathione and a size range of its
conjugates. All inhibitor concentrations are 0.2 mmol l–1;
sample sizes are 6 tubules, except for `no inhibitor, which represents all
control trials (N=23). *Change in uptake rate (second
measurement period relative to first measurement period) in presence of
inhibitor significantly different from uptake rate in absence of inhibitor;
P<0.05, paired t-test.
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Fig. 5. FL accumulation in Malpighian tubules of Drosophila, and its
inhibition by several potential substrates. N=3 tubules for each.
PBD, 3-phenobenzoic acid (1 mmol l–1); PAH,
p-aminohippuyric acid (3 mmol l–1); PBA, probenecid
(0.5 mmol l–1). *Change in uptake rate (second
measurement period relative to first measurement period) in presence of
inhibitor significantly different from uptake rate in absence of inhibitor;
P<0.05, paired t-test.
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Fig. 6. Uptake of insecticide metabolites 3-phenoxybenzoic acid (PBA) and malathion
monocarboxylic acid (MMA) in Malpighian tubule bundles, as detected by HPLC.
Uptake in presence of inhibitor conditions (FL, 2 mmol l–1;
PBD, 10 mmol l–1; or water pre-exposure) is plotted relative
to control uptake (uptake with metabolite alone in Ringer's). N=4
samples for each. *Uptake of metabolite in presence of inhibitor
condition significantly different from uptake in absence of inhibitor
condition.
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Fig. 7. Primary metabolic fates known for malathion in animal tissues (including
insects).
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© The Company of Biologists Ltd 2005
