title: Ca(2+)-activated Cl- currents in pulmonary arterial myocytes.
abstract: Currents from smooth muscle cells isolated from the pulmonary arterial tree of the rat were recorded under voltage clamp using the whole cell configuration of the patch-clamp technique. Rapid increases in cytosolic free calcium evoked by flash photolysis of Nitr-5 activated a current that, following ion substitution and pharmacological experiments, proved to be carried by Cl-. This current [ICl(Ca)] was evoked independently of photolytic by-products and, although smaller, was still activated in the absence of pipette ATP. Experiments revealed that ICl(Ca) was evoked in 80% in the cells isolated from the main pulmonary artery but only in 43% of the cells isolated from small vessels (200-400 microns ID). Application of caffeine also resulted in activation of ICl(ca), although the response current magnitude was larger in the main pulmonary artery. Photolysis of Nitr-5 still activated ICl(ca) in the presence of caffeine, suggesting that Ca2-release is not a prerequisite for activation of ICl(ca). These results represents in the first electrophysiological recordings of Cl- currents from small pulmonary arterial vessels and indicate that their Ca2+ regulation and/or distribution may be different throughout the pulmonary circulation.
authors.affiliation: Department of Pharmacology, Oxford University, United Kingdom.
authors.forename: L H
authors.initials: LH
authors.lastname: Clapp
authors.forename: J L
authors.initials: JL
authors.lastname: Turner
authors.forename: R Z
authors.initials: RZ
authors.lastname: Kozlowski
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002614:Chelating Agents; D002712:Chlorides / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives; D004553:Electric Conductivity; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D011651:Pulmonary Artery / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002614:Chelating Agents; D002712:Chlorides; C052455:nitr 5; D004533:Egtazic Acid; D002118:Calcium