Cyclic GMP regulation of the L-type Ca2+ channel current in human atrial myocytes

Authors


  • Authors' present addresses

    I. Verde: Faculdade de Ciências da Saúde, Universidade da Beira Interior, Rua Marquês d'Ávila e Bolama, 6201-001 Covilhã, Portugal.

    C. Rücker-Martin: Laboratoire de Physiologie Cardiovasculaire et Thymique, CNRS ERS 566, Université de Paris-Sud, Hôpital Marie-Lannelongue, F-92350 Le Plessis Robinson, France.

Corresponding author R. Fischmeister: INSERM U-446, Université de Paris-Sud, Faculté de Pharmacie, 5 rue Jean-Baptiste Clément, F-92296 Châtenay-Malabry Cedex, France. Email: fisch@vjf.inserm.fr

Abstract

  • The regulation of the L-type Ca2+ current (ICa) by intracellular cGMP was investigated in human atrial myocytes using the whole-cell patch-clamp technique.

  • Intracellular application of 0.5 μm cGMP produced a strong stimulation of basal ICa (+64 ± 5%, n= 60), whereas a 10-fold higher cGMP concentration induced a 2-fold smaller increase (+36 ± 8%, n= 35).

  • The biphasic response of ICa to cGMP was not mimicked by the cGMP-dependent protein kinase (PKG) activator 8-bromoguanosine 3′,5′ cyclic monophosphate (8-bromo-cGMP, 0.5 or 5 μm), and was not affected by the PKG inhibitor KT 5823 (100 nm).

  • In contrast, cGMP stimulation of ICa was abolished by intracellular perfusion with PKI (10 μm), a selective inhibitor of the cAMP-dependent protein kinase (PKA).

  • Selective inhibition of the cGMP-inhibited phosphodiesterase (PDE3) by extracellular cilostamide (100 nm) strongly enhanced basal ICa in control conditions (+78 ± 13%, n= 7) but had only a marginal effect in the presence of intracellular cGMP (+22 ± 7% in addition to 0.5 μm cGMP, n= 11; +20 ± 22% in addition to 5 μm cGMP, n= 7).

  • Application of erythro-9-[2-hydroxy-3-nonyl]adenine (EHNA, 30 μm), a selective inhibitor of the cGMP-stimulated phosphodiesterase (PDE2), fully reversed the secondary inhibitory effect of 5 μm cGMP on ICa (+99 ± 16% stimulation, n= 7).

  • Altogether, these data indicate that intracellular cGMP regulates basal ICa in human atrial myocytes in a similar manner to NO donors. The effect of cGMP involves modulation of the cAMP level and PKA activity via opposite actions of the nucleotide on PDE2 and PDE3.

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