title: K⁺ absorption by locust gut and inhibition of ileal K⁺ and water transport by FGLamide allatostatins.
abstract: The scanning ion-selective electrode technique (SIET) was utilized for the first time in Locusta migratoria to characterize K(+) transport along the digestive tract and to determine the effect of two locust FGLamide allatostatins (FGLa/ASTs) on K(+) transport: a previously sequenced FGLa/AST from Schistocerca gregaria (Scg-AST-6; ARPYSFGL-NH2) and a newly sequenced FGLa/AST from L. migratoria (Locmi-FGLa/AST-2; LPVYNFGL-NH2). Regional differences in K(+) fluxes along the gut were evident, where K(+) efflux in vitro (or absorption into the hemolymph in vivo) was greatest at the anterior ileum, and lowest at the colon. Ileal K(+) efflux was inhibited by both Scg-AST-6 and Locmi-FGLa/AST-2, with maximal inhibition at 10(-10) and 10(-11) mol l(-1), respectively. Both FGLa/ASTs also inhibited cAMP-stimulated K(+) efflux from the ileum. Locmi-FGLa/AST-2 also inhibited efflux of water across the ileum. Locusts are terrestrial insects living in dry climates, risking desiccation and making water conservation a necessity. The results suggest that FGLa/ASTs may be acting as diuretics by increasing K(+) excretion and therefore increasing water excretion. Thus it is likely that FGLa/ASTs are involved in the control of hemolymph water and ion levels during feeding and digestion, to help the locust deal with the excess K(+) load (and subsequently fluid) when the meal is processed.
authors.affiliation: Department of Biology, York University, Toronto, ON, Canada, M3J 1P3.
authors.forename: Lisa
authors.initials: L
authors.lastname: Robertson
authors.affiliation: Department of Biology, York University, Toronto, ON, Canada, M3J 1P3.
authors.forename: Andrew
authors.initials: A
authors.lastname: Donini
authors.affiliation: Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada, L5L 1C6 angela.lange@utoronto.ca.
authors.forename: Angela B
authors.initials: AB
authors.lastname: Lange
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D041981:Gastrointestinal Tract / Q000378:metabolism*; D048188:Locusta migratoria / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D009479:Neuropeptides; D014867:Water; C076523:allatostatin; D011188:Potassium
keywords: FGLa/AST; Hindgut; Ileum; Ion; Locusta migratoria; Matrix-assisted laser desorption/ionization time-of-flight; Peptide; Scanning ion-selective electrode technique; Second messenger; Sequencing; cAMP