Ca2+-activated cl- currents in pulmonary arterial myocytes.
Clapp, Lucie H., Joanne L. Turner, and Roland Z. Kozlowski.
University Department of Pharmacology, Mansfield Road, Oxford, OX1
3QT & *Cardiovascular Research, The Rayne Institute, St. Thomas'
Hospital, London, SE1 7EH, UK
APStracts 2:0469H, 1995.
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 [Ca2+]i evoked by flash photolysis of nitr-5
activated a current which, following ion substitution and
pharmacological experiments, proved to be carried by Cl- ions. This
current (ICl(Ca)) was evoked independently of photolytic bi-products
and, although smaller, was still activated in the absence of pipette
ATP. Experiments revealed that ICl(Ca) was evoked in 80% of cells
isolated from the main pulmonary artery but only in 43% of the cells
isolated from small vessels (internal diameter 200-400 [mu]m).
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 represent 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.
Received 20 February 1995; accepted in final form 26 September
1995.
APS Manuscript Number H155-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95