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  • Title: ATP activates K and Cl channels via purinoceptor-mediated release of Ca2+ in human coronary artery smooth muscle.
    Author: Strøbaek D, Christophersen P, Dissing S, Olesen SP.
    Journal: Am J Physiol; 1996 Nov; 271(5 Pt 1):C1463-71. PubMed ID: 8944628.
    Abstract:
    Coronary artery smooth muscle cells express G protein-coupled purinoceptors, and we report here for the first time how receptor activation by extracellular ATP influences cell membrane currents and membrane potential in human cells. ATP (100 microM) stimulated a triphasic change in membrane potential lasting several seconds, which was caused by sequential opening of transient inward and outward conductances. The inward current was carried by Cl- and the outward current by K+, as shown by ion substitution and changes in holding potential. Both currents were independent of the presence of external Ca2+ but were blocked by strong buffering of Ca2+ in the internal solution. The P2u- and P2y-purinoceptor agonists UTP and 2-methylthioadenosine 5'-triphosphate activated similar currents, whereas the P2x-receptor agonist alpha, beta-methyleneadenosine 5'-triphosphate and the P1-receptor agonist adenosine failed to stimulate any whole cell currents. The ATP-activated K+ current was inhibited by iberiotoxin (200 nM), and it was potentiated by the BK channel activator NS-1619 (30 microM). In cell-attached recordings, ATP activated a 230-pS BK channel. In conclusion, ATP acting via P2 purinoceptors stimulated release of Ca2+ from internal stores and transiently activated depolarizing Cl- and hyperpolarizing BK channels in human coronary artery smooth muscle cells.
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