Transport of H(+), Na(+) and K(+) Across the Posterior Midgut of Blood-Fed Mosquitoes (Aedes Aegypti)

J Insect Physiol. 2014 Feb;61:42-50. doi: 10.1016/j.jinsphys.2013.12.008. Epub 2014 Jan 7.

Abstract

Following ingestion of a blood meal, the adult female mosquito undergoes a massive diuresis during which Na(+), Cl(-) and water are secreted at high rates by the Malpighian tubules. In the hours following completion of diuresis, digestion of the K(+)-rich blood cells provides a source of energy as well as amino acids for proteins in the developing eggs. Although the transport of inorganic ions by the Malpighian tubules of blood-fed mosquitoes has been extensively characterized, relatively little is known of the epithelial transport mechanisms responsible for movement of Na(+), H(+), and K(+) across the posterior midgut. In this paper we have used the Scanning Ion-selective Electrode Technique (SIET) to measure the basal (unstimulated) rates of transport of K(+), Na(+) and H(+) across the isolated posterior midgut at intervals after the blood meal. We have also measured luminal concentrations of Na(+) and K(+) and the transepithelial electrical potential at the same time points and have calculated the electrochemical potentials for Na(+), K(+) and H(+) across the midgut. SIET measurements reveal absorption (lumen to bath) of Na(+) and H(+) and secretion of K(+) for the first 2h after blood-feeding. By 24h after the meal, absorption of Na(+) and H(+) remains active while there is an electrochemical gradient favouring absorption of K(+). Inhibition by ouabain and Ba(2+) suggest a role for the Na(+)/K(+)-ATPase and K(+) channels in absorption of Na(+) and K(+), respectively. Inhibition of H(+) absorption by acetazolamide implicates carbonic anhydrase in transepithelial H(+) transport.

Keywords: Blood-feeding; Epithelial transport; Midgut; Mosquito; Na(+)/K(+)-ATPase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aedes / metabolism*
  • Animals
  • Barium / pharmacology
  • Biological Transport, Active / drug effects
  • Enzyme Inhibitors / pharmacology
  • Female
  • Gastrointestinal Tract / metabolism
  • Hydrogen / metabolism*
  • Ion Transport / drug effects
  • Ion-Selective Electrodes
  • Ouabain / pharmacology
  • Potassium / blood
  • Potassium / metabolism*
  • Sodium / blood
  • Sodium / metabolism*
  • Sodium-Potassium-Exchanging ATPase / metabolism
  • Time Factors

Substances

  • Enzyme Inhibitors
  • Barium
  • Ouabain
  • Hydrogen
  • Sodium
  • Sodium-Potassium-Exchanging ATPase
  • Potassium