Alkalinization in the isolated and perfused anterior midgut of the larval mosquito, Aedes aegypti

J Insect Sci. 2008;8:1-20. doi: 10.1673/031.008.4601.

Abstract

In the present study, isolated midguts of larval Aedes aegypti L. (Diptera: Culicidae) were mounted on perfusion pipettes and bathed in high buffer mosquito saline. With low buffer perfusion saline, containing m-cresol purple, transepithelial voltage was monitored and luminal alkalinization became visible through color changes of m-cresol purple after perfusion stop. Lumen negative voltage and alkalinization depended on metabolic energy and were stimulated in the presence of serotonin (0.2 micromol l(-1)). In some experiments a pH microelectrode in the lumen recorded pH values up to 10 within minutes after perfusion stop. The V-ATPase inhibitor concanamycin (50 micromol l(-1)) on the hemolymph side almost abolished V(te) and inhibited luminal alkalinization. The carbonic anhydrase inhibitor, methazolamide (50 micromol l(-1)), on either the luminal or hemolymph-side, or the inhibitor of anion transport, DIDS (1 mmol l(-1)) on the luminal side, had no effect on V(te) or alkalinization. Cl(-) substitution in the lumen or on both sides of the tissue affected V(te), but the color change of m-cresol purple was unchanged from control conditions. Hemolymph-side Na(+) substitution or addition of the Na(+)/H(+) exchange inhibitor, amiloride (200 micromol l(-1)), reduced V(te) and luminal alkalinization. Luminal amiloride (200 micromol l(-1)) was without effects on V(te) or alkalinization. High K(+) (60 mmol l(-1)) in the lumen reduced V(te) without affecting alkalinization. These results indicate that strong luminal alkalinization in isolated and perfused anterior midgut of larval A. aegypti depends on basolateral V-ATPase, but is apparently independent of carbonic anhydrase, apical Cl(-)/HCO(3)(-) exchange or apical K(+)/2H(+) antiport.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Aedes / drug effects
  • Aedes / physiology*
  • Amiloride / pharmacology
  • Animals
  • Enzyme Inhibitors / pharmacology
  • Gastrointestinal Tract / metabolism
  • Hemolymph / physiology
  • Hydrogen-Ion Concentration
  • Larva
  • Macrolides / pharmacology
  • Methazolamide / pharmacology
  • Serotonin / pharmacology
  • Sodium / metabolism
  • Sodium Channel Blockers / pharmacology
  • Time Factors

Substances

  • Enzyme Inhibitors
  • Macrolides
  • Sodium Channel Blockers
  • Serotonin
  • Amiloride
  • Sodium
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
  • Methazolamide