Article date: February 2001
By: Patricia Viard, Nathalie Macrez, Chantal Mironneau, Jean Mironneau in Volume 132, Issue 3, pages 669-676
Previous data have shown that activation of β3‐adrenoceptors stimulates vascular L‐type Ca2+ channels through a Gαs‐induced stimulation of the cyclic AMP/PKA pathway. The present study investigated whether β‐adrenergic stimulation also uses the Gβγ/PI3K/PKC pathway to modulate L‐type Ca2+ channels in rat portal vein myocytes.
Peak Ba2+ current (IBa) measured using the whole‐cell patch clamp method was maximally increased by application of 10 μM isoprenaline after blockade of β3‐adrenoceptors by 1 μM SR59230A. Under these conditions, the isoprenaline‐induced stimulation of IBa was reversed by ICI‐118551 (a specific β2‐adrenoceptor antagonist) but not by atenolol (a specific β1‐adrenoceptor antagonist). The β2‐adrenoceptor agonist salbutamol increased IBa, an effect which was reversed by ICI‐118551 whereas the β1‐adrenoceptor agonist dobutamine had no effect on IBa.
Application of PKA inhibitors (H‐89 and Rp 8‐Br‐cyclic AMPs) or a PKC inhibitor (calphostin C) alone did not affect the β2‐adrenergic stimulation of IBa whereas simultaneous application of both PKA and PKC inhibitors completely blocked this stimulation.
The β2‐adrenergic stimulation of L‐type Ca2+ channels was blocked by a pre‐treatment with cholera toxin and by intracellular application of an anti‐Gαs antibody (directed against the carboxyl terminus of Gαs). In the presence of H‐89, intracellular infusion of an anti‐Gβcom antibody or a βARK1 peptide as well as a pre‐treatment with wortmannin (a PI3K inhibitor) blocked the β2‐adrenergic stimulation of IBa.
These results suggest that the β2‐adrenergic stimulation of vascular L‐type Ca2+ channels involves both Gαs and Gβγ subunits which exert their stimulatory effects through PKA and PI3K/PKC pathways, respectively.
Previous data have shown that activation of β3‐adrenoceptors stimulates vascular L‐type Ca2+ channels through a Gαs‐induced stimulation of the cyclic AMP/PKA pathway. The present study investigated whether β‐adrenergic stimulation also uses the Gβγ/PI3K/PKC pathway to modulate L‐type Ca2+ channels in rat portal vein myocytes.
Peak Ba2+ current (IBa) measured using the whole‐cell patch clamp method was maximally increased by application of 10 μM isoprenaline after blockade of β3‐adrenoceptors by 1 μM SR59230A. Under these conditions, the isoprenaline‐induced stimulation of IBa was reversed by ICI‐118551 (a specific β2‐adrenoceptor antagonist) but not by atenolol (a specific β1‐adrenoceptor antagonist). The β2‐adrenoceptor agonist salbutamol increased IBa, an effect which was reversed by ICI‐118551 whereas the β1‐adrenoceptor agonist dobutamine had no effect on IBa.
Application of PKA inhibitors (H‐89 and Rp 8‐Br‐cyclic AMPs) or a PKC inhibitor (calphostin C) alone did not affect the β2‐adrenergic stimulation of IBa whereas simultaneous application of both PKA and PKC inhibitors completely blocked this stimulation.
The β2‐adrenergic stimulation of L‐type Ca2+ channels was blocked by a pre‐treatment with cholera toxin and by intracellular application of an anti‐Gαs antibody (directed against the carboxyl terminus of Gαs). In the presence of H‐89, intracellular infusion of an anti‐Gβcom antibody or a βARK1 peptide as well as a pre‐treatment with wortmannin (a PI3K inhibitor) blocked the β2‐adrenergic stimulation of IBa.
These results suggest that the β2‐adrenergic stimulation of vascular L‐type Ca2+ channels involves both Gαs and Gβγ subunits which exert their stimulatory effects through PKA and PI3K/PKC pathways, respectively.
British Journal of Pharmacology (2001) 132, 669–676; doi:10.1038/sj.bjp.0703864
DOI: 10.1038/sj.bjp.0703864
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