title: Transport of H(+), Na(+) and K(+) across the posterior midgut of blood-fed mosquitoes (Aedes aegypti).
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.
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton L8S 4K1, Canada.
authors.forename: Evan K
authors.initials: EK
authors.lastname: Pacey
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton L8S 4K1, Canada. Electronic address: odonnell@mcmaster.ca.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Donnell
mesh_terms: D000330:Aedes / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D041981:Gastrointestinal Tract / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D017736:Ion-Selective Electrodes; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood / Q000378:metabolism*; D012964:Sodium / Q000097:blood / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D001464:Barium; D010042:Ouabain; D006859:Hydrogen; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium
keywords: Blood-feeding; Epithelial transport; Midgut; Mosquito; Na(+)/K(+)-ATPase