Calcium-dependence of the calcium-activated chloride current in smooth muscle cells of rat portal vein.
Ca(2+)-activated Cl- current in freshly isolated smooth muscle cells from rat portal vein was studied using the whole-cell patch-clamp technique. Simultaneously, the free-cytosolic Ca2+ concentration (Cai) was estimated using emission from the dye Indo-1. Pretreatment of the cells with amytal and carbonyl-cyanide-m-chlorophenylhydrazone, which reduced the intracellular adenosine triphosphate concentration, was used to weaken the cellular Ca2+ homeostatic system. Cai of treated cells slowly increased during perfusion with an external Ca(2+)-containing solution. This rise in Cai gradually activated a Ca(2+)-dependent Cl- current which allowed the study of the relationship between activation of this current and Cai levels. The threshold Cai for activation of Cl- channels was around 180 nM and full activation occurred at 600 nM. The Cai dependence of the Cl- channels was not changed during application of noradrenaline and did not depend on the membrane potential. The gating of Ca(2+)-dependent Cl- channels of rat portal vein myocytes seems to be mainly controlled by intracellular Ca2+.
Pacaud
P
P
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, C.N.R.S. URA 1489, Bordeaux, France.
Loirand
G
G
Grégoire
G
G
Mironneau
C
C
Mironneau
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011169:Portal Vein / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D002712:Chlorides; D007473:Ion Channels; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002118:Calcium; D009638:Norepinephrine