Ca2+ entry following P2X receptor activation induces IP3 receptor-mediated Ca2+ release in myocytes from small renal arteries

Authors

  • Oleksandr V Povstyan,

    1. Division of Basic Medical Sciences, St. George's, University of London, London, UK
    2. Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine
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  • Maksym I Harhun,

    1. Division of Basic Medical Sciences, St. George's, University of London, London, UK
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  • Dmitri V Gordienko

    Corresponding author
    1. Division of Basic Medical Sciences, St. George's, University of London, London, UK
    2. Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine
      Dr Dmitri Gordienko, Ion Channels and Cell Signalling Centre, Division of Basic Medical Sciences, St. George's, University of London, Cranmer Terrace, London SW17 0RE, UK. E-mail: gordienk@sgul.ac.uk
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Dr Dmitri Gordienko, Ion Channels and Cell Signalling Centre, Division of Basic Medical Sciences, St. George's, University of London, Cranmer Terrace, London SW17 0RE, UK. E-mail: gordienk@sgul.ac.uk

Abstract

BACKGROUND AND PURPOSE P2X receptors mediate sympathetic control and autoregulation of the renal circulation triggering contraction of renal vascular smooth muscle cells (RVSMCs) via an elevation of intracellular Ca2+ concentration ([Ca2+]i). Although it is well-appreciated that the myocyte Ca2+ signalling system is composed of microdomains, little is known about the structure of the [Ca2+]i responses induced by P2X receptor stimulation in vascular myocytes.

EXPERIMENTAL APPROACHES Using confocal microscopy, perforated-patch electrical recordings, immuno-/organelle-specific staining, flash photolysis and RT-PCR analysis we explored, at the subcellular level, the Ca2+ signalling system engaged in RVSMCs on stimulation of P2X receptors with the selective agonist αβ-methylene ATP (αβ-meATP).

KEY RESULTS RT-PCR analysis of single RVSMCs showed the presence of genes encoding inositol 1,4,5-trisphosphate receptor type 1(IP3R1) and ryanodine receptor type 2 (RyR2). The amplitude of the [Ca2+]i transients depended on αβ-meATP concentration. Depolarization induced by 10 µmol·L−1αβ-meATP triggered an abrupt Ca2+ release from sub-plasmalemmal (‘junctional’) sarcoplasmic reticulum enriched with IP3Rs but poor in RyRs. Depletion of calcium stores, block of voltage-gated Ca2+ channels (VGCCs) or IP3Rs suppressed the sub-plasmalemmal [Ca2+]i upstroke significantly more than block of RyRs. The effect of calcium store depletion or IP3R inhibition on the sub-plasmalemmal [Ca2+]i upstroke was attenuated following block of VGCCs.

CONCLUSIONS AND IMPLICATIONS Depolarization of RVSMCs following P2X receptor activation induces IP3R-mediated Ca2+ release from sub-plasmalemmal (‘junctional’) sarcoplasmic reticulum, which is activated mainly by Ca2+ influx through VGCCs. This mechanism provides convergence of signalling pathways engaged in electromechanical and pharmacomechanical coupling in renal vascular myocytes.

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