title: Serotonin triggers cAMP and PKA-mediated intracellular calcium waves in Malpighian tubules of Rhodnius prolixus.
abstract: Rhodnius prolixus is a hematophagous insect vector of Chagas disease capable of ingesting up to 10 times its unfed body weight in blood in a single meal. The excess water and ions ingested with the meal are expelled through a rapid postprandial diuresis driven by the Malpighian tubules. Diuresis is triggered by at least two diuretic hormones, a CRF-related peptide and serotonin, which were traditionally believed to trigger cAMP as an intracellular second messenger. Recently, calcium has been suggested to act as a second messenger in serotonin-stimulated Malpighian tubules. Thus, we tested the role of calcium in serotonin-stimulated Malpighian tubules from R. prolixus. Our results show that serotonin triggers cAMP-mediated intracellular Ca(2+) waves that were blocked by incubation in Ca(2+)-free saline containing the cell membrane-permeant Ca(2+) chelator BAPTA-AM, or the PKA blocker H-89. Treatment with 8-Br-cAMP triggered Ca(2+) waves that were blocked by H-89 and BAPTA-AM. Analysis of the secreted fluid in BAPTA-AM-treated tubules showed a 75% reduction in fluid secretion rate with increased K(+) concentration, reduced Na(+) concentration. Taken together, the results indicate that serotonin triggers cAMP and PKA-mediated Ca(2+) waves that are required for maximal ion transport rate.
authors.affiliation: Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Paula
authors.initials: P
authors.lastname: Gioino
authors.affiliation: Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Brendan G
authors.initials: BG
authors.lastname: Murray
authors.affiliation: Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada juan.ianowski@usask.ca.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Ianowski
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007301:Insect Hormones / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects* / Q000502:physiology; D007546:Isoquinolines / Q000494:pharmacology; D008317:Malpighian Tubules / Q000378:metabolism*; D012239:Rhodnius; D012701:Serotonin / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D007301:Insect Hormones; D007546:Isoquinolines; D013449:Sulfonamides; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D015124:8-Bromo Cyclic Adenosine Monophosphate; D012701:Serotonin; D004533:Egtazic Acid; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium
keywords: Malpighian tubule; Rhodnius prolixus; calcium waves; intracellular calcium