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Beta-2 adrenergic activation of L-type Ca++ current in cardiac myocytes.

Abstract : The whole-cell patch-clamp and intracellular perfusion techniques were used for studying the effects of a beta-2 adrenergic receptor activation on the L-type Ca current (ICa) in frog ventricular myocytes. Thebeta-2 adrenergic agonist zinterol increasedICa in a concentration-dependent manner with an EC50 (i.e., the concentration of zinterol at which the response was 50% of the maximum) of 2.2 nM. The effect of zinterol was essentially independent of the membrane potential. The stimulatory effect of zinterol was competitively antagonized by ICI 118,551, a beta-2 adrenergic antagonist. The maximal stimulatory effect of zinterol was comparable in amplitude to the effect of a saturating concentration (1 or 10 μM) of isoprenaline, a nonselective beta adrenergic agonist. Moreover, 3-isobutyl-1-methylxanthine (100 μM), a nonselective phosphodiesterase inhibitor, or forskolin (10 μM), a direct activator of adenylyl cyclase, had no additive effects in the presence of 0.1 μM zinterol. Zinterol had a long lasting action on frogICa because after washout of the drug,ICa returned to basal level with a time constant of 17 min. An application of acetylcholine (1 μM) during this recovery phase promptly reduced ICaback to its basal level suggesting a persistent activation of adenylyl cyclase due to a slow dissociation rate constant of zinterol from its receptor. Zinterol also increased ICa in rat ventricular and human atrial myocytes, and the maximal effect was obtained at 10 and 1 μM, respectively. In all three preparations, intracellular perfusion with 20 μM PKI(15–22), a highly selective peptide inhibitor of cAMP-dependent protein kinase, completely antagonized the stimulatory effect of zinterol onICa. We conclude that beta-2 adrenergic receptor activation produces a strong increase inICa in frog, rat and human cardiac myocytes which is due to stimulation of adenylyl cyclase and activation of cAMP-dependent phosphorylation.
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Submitted on : Wednesday, March 23, 2022 - 10:46:24 AM
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  • HAL Id : hal-03617022, version 1
  • PUBMED : 9353357

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V Skeberdis, J Jurevicius, Rodolphe Fischmeister. Beta-2 adrenergic activation of L-type Ca++ current in cardiac myocytes.. Journal of Pharmacology and Experimental Therapeutics, American Society for Pharmacology and Experimental Therapeutics, 1997, 283 (2), pp.452-61. ⟨hal-03617022⟩

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