title: Leucokinin activates Ca(2+)-dependent signal pathway in principal cells of Aedes aegypti Malpighian tubules.
abstract: The role of Ca(2+) in mediating the diuretic effects of leucokinin-VIII was studied in isolated perfused Malpighian tubules of the yellow fever mosquito, Aedes aegypti. Peritubular leucokinin-VIII (1 microM) decreased the transepithelial resistance from 11.2 to 2.6 kOmega. cm, lowered the transepithelial voltage from 42.8 to 2.7 mV, and increased transepithelial Cl(-) diffusion potentials 5.1-fold. In principal cells of the tubules, leucokinin-VIII decreased the fractional resistance of the basolateral membrane from 0.733 to 0.518. These effects were reversed by the peritubular Ca(2+)-channel blocker nifedipine, suggesting a role of peritubular Ca(2+) and basolateral Ca(2+) channels in signal transduction. In Ca(2+)-free Ringer bath, the effects of leucokinin-VIII were partial and transient but were fully restored after the bath Ca(2+) concentration was restored. Increasing intracellular Ca(2+) with thapsigargin duplicated the effects of leucokinin-VIII, provided that peritubular Ca(2+) was present. The kinetics of the effects of leucokinin-VIII is faster than that of thapsigargin, suggesting the activation of inositol-1,4,5-trisphosphate-receptor channels of intracellular stores. Store depletion may then bring about Ca(2+) entry into principal cells via nifedipine-sensitive Ca(2+) channels in the basolateral membrane.
authors.affiliation: Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Ming-Jiun
authors.initials: MJ
authors.lastname: Yu
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Beyenbach
mesh_terms: D000330:Aedes / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D003058:Cockroaches; D004232:Diuretics / Q000494:pharmacology; D017097:Electric Impedance; D004594:Electrophysiology; D019476:Insect Proteins / Q000494:pharmacology*; D007700:Kinetics; D008317:Malpighian Tubules / Q000187:drug effects* / Q000378:metabolism*; D009479:Neuropeptides / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004232:Diuretics; D019476:Insect Proteins; D009479:Neuropeptides; D015221:Potassium Channels; D001464:Barium; D019284:Thapsigargin; D009543:Nifedipine; D002118:Calcium