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First published online January 16, 2009
Journal of Experimental Biology 212, 373-377 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.023580
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Revisiting the cellular mechanisms of strong luminal alkalinization in the anterior midgut of larval mosquitoes

Horst Onken1,* and David F. Moffett2

1 Department of Biological Sciences, Wagner College, Staten Island, NY 10301, USA
2 School of Biological Sciences, Washington State University, Pullman, WA 99164, USA


Figure 1
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  		Fig. 1. Transepithelial profiles of the proton-motive force (in mV) calculated from the average membrane voltages and transmembrane pH gradients for (A) a control condition with mosquito saline of pH 7 on both sides of the tissue, (B) after stimulation with serotonin (pH=7 on both sides; lumen 100 mmol l–1 NaCl) and (C) after increasing the pH of the luminal perfusate to 10. HL, hemolymph; L, lumen.

 

Figure 2
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  		Fig. 2. Model of hypothetical transport mechanisms involved in strong alkalinization based on earlier proposals (Boudko et al., 2001Go; Onken et al., 2004Go), focusing on anionic pathways in the apical membrane. CA, carbonic anhydrase.

 

Figure 3
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  		Fig. 3. Mean lumen negative transepithelial voltages (Vte; –s.e.m.) of six anterior midguts stimulated with serotonin (0.2 µmol l–1) in the presence (gray bar) and absence (white bar) of luminal methazolamide (200 µmol l–1), and photographs of a representative preparation of the anterior midgut of larval (fourth instar) Aedes aegypti at identical times after perfusion stop in the presence (right) and absence (left) of luminal methazolamide (200 µmol l–1). [Figure reproduced from Onken and colleagues (Onken et al., 2008Go).]

 

Figure 4
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  		Fig. 4. Model of hypothetical transport mechanisms involved in strong alkalinization and amino acid absorption based on earlier proposals (Okech et al., 2008Go; Patrick et al., 2006Go), focusing on cationic pathways in the apical membrane.

 

Figure 5
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  		Fig. 5. Mean lumen negative transepithelial voltages (Vte; –s.e.m.) of five anterior midguts stimulated with serotonin (0.2 µmol l–1) in the presence (gray bar) and absence (white bar) of luminal amiloride (200 µmol l–1), and photographs of a representative preparation of the anterior midgut of larval (fourth instar) Aedes aegypti at identical times after perfusion stop in the presence (right) and absence (left) of luminal amiloride (200 µmol l–1). [Figure reproduced from Onken and colleagues (Onken et al., 2008Go).]

 

Figure 6
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  		Fig. 6. Representative time-course of the lumen negative transepithelial voltage (Vte) of the anterior midgut of larval (fourth instar) Aedes aegypti in the presence of hemolymph-side mosquito saline and luminal 100 mmol l–1 NaCl. After mounting of the tissue, Vte declines but successively recovers after addition of serotonin (0.2 µmol l–1) to the hemolymph-side bath and glutamine (10 mmol l–1) to the luminal perfusate. Washout of serotonin in the presence of luminal glutamine indicates that the effect of luminal glutamine is stimulated by serotonin.

 

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