G protein-mediated inhibitory effect of a nitric oxide donor on the L-type Ca2+ current in rat ventricular myocytes.
1. The role of the cGMP pathway in the modulation of the cardiac L-type Ca2+ current (ICa,L) by nitric oxide (NO) was examined in rat ventricular myocytes. 2. The NO donors DEANO, SIN-1, SNP, SNAP and GSNO had no significant effects on basal ICa,L. However, DEANO (100 microM) inhibited ICa,L after the current had been previously stimulated by either isoprenaline (Iso, 1-10 nM), a beta-adrenergic agonist, or isobutylmethyl-xanthine (IBMX, 10-80 microM), a wide spectrum phosphodiesterase (PDE) inhibitor. 3. The anti-adrenergic effect of DEANO on ICa,L was not mimicked by other NO donors (SIN-1, SNAP and SPNO). 4. The NO-sensitive guanylyl cyclase inhibitor ODQ (10 microM), antagonized the inhibitory effect of DEANO on ICa,L. Likewise, inhibitors of the cGMP-dependent protein kinase (cG-PK), Rp-8-chloro-phenylthio-cGMP (10 microM) and KT5823 (0.1 and 0.3 microM), also abolished the inhibitory effect of DEANO on Iso (1-10 nM)-stimulated ICa,L. 5. Intracellular dialysis with exogenous cAMP (10-100 microM) blunted the inhibitory effect of DEANO (10 and 100 microM) on ICa,L. SNAP and SNP also had no effect on the cAMP-stimulated ICa,L. 6. Pre-treatment of the myocytes with pertussis toxin (0.5 microg ml-1, 4-6 h at 37 degrees C) eliminated the inhibitory effect of DEANO (100 microM) on ICa,L, in the presence of either Iso (0.01 and 1 nM) or IBMX (10-80 microM). 7. These results demonstrate that DEANO produces anti-adrenergic effects in rat ventricular myocytes. This effect of DEANO occurs in a cGMP-dependent manner, and involves activation of cG-PK and regulation of a pertussis toxin-sensitive G protein.
Abi-Gerges
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Laboratoire de Cardiologie Cellulaire & Moleculaire, INSERM U-446, Faculte de Pharmacie, Universite Paris-Sud, F-92296 Châtenay-Malabry, France. naja.abi-g@cep.u-psud.fr
Fischmeister
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Méry
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D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000502:physiology*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D017551:Microdialysis; D009206:Myocardium / Q000166:cytology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020030:Nitric Oxide Donors; D019204:GTP-Binding Proteins; D006162:Guanylate Cyclase