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Beta 2-adrenergic receptor signaling acts via NO release to mediate ACh-induced activation of ATP-sensitive K+ current in cat atrial myocytes.

Wang YG, Dedkova EN, Steinberg SF, Blatter LA, Lipsius SL - J. Gen. Physiol. (2002)

Bottom Line: Wortmannin (0.2 microM) or LY294002 (10 microM), inhibitors of phosphatidylinositol 3'-kinase (PI-3K), abolished the effects of zinterol to both mediate ACh-activated I(K,ATP) and stimulate [NO](i).We conclude that both beta(1)- and beta(2)-ARs stimulate cAMP. beta(2)-ARs act via two signaling pathways to stimulate cAMP, one of which is mediated via G(i)-protein and PI-3K coupled to NO-cGMP signaling.The differential effects of beta(1)- and beta(2)-ARs can be explained by the coupling of these two beta-ARs to different effector signaling pathways.

View Article: PubMed Central - PubMed

Affiliation: Stritch School of Medicine, Department of Physiology, Loyola University Medical Center, 2160 South First Avenue, Maywood, IL 60153, USA.

ABSTRACT
In atrial myocytes, an initial exposure to isoproterenol (ISO) acts via cAMP to mediate a subsequent acetylcholine (ACh)-induced activation of ATP-sensitive K(+) current (I(K,ATP)). In addition, beta-adrenergic receptor (beta-AR) stimulation activates nitric oxide (NO) release. The present study determined whether the conditioning effect of beta-AR stimulation acts via beta(1)- and/or beta(2)-ARs and whether it is mediated via NO signaling. 0.1 microM ISO plus ICI 118,551 (ISO-beta(1)-AR stimulation) or ISO plus atenolol (ISO-beta(2)-AR stimulation) both increased L-type Ca(2+) current (I(Ca,L)) markedly, but only ISO-beta(2)-AR stimulation mediated ACh-induced activation of I(K,ATP). 1 microM zinterol (beta(2)-AR agonist) also increased I(Ca,L) and mediated ACh-activated I(K,ATP). Inhibition of NO synthase (10 microM L-NIO), guanylate cyclase (10 microM ODQ), or cAMP-PKA (50 microM Rp-cAMPs) attenuated zinterol-induced stimulation of I(Ca,L) and abolished ACh-activated I(K,ATP). Spermine-NO (100 microM; an NO donor) mimicked beta(2)-AR stimulation, and its effects were abolished by Rp-cAMPs. Intracellular dialysis of 20 microM protein kinase inhibitory peptide (PKI) abolished zinterol-induced stimulation of I(Ca,L). Measurements of intracellular NO ([NO](i)) using the fluorescent indicator DAF-2 showed that ISO-beta(2)-AR stimulation or zinterol increased [NO](i). L-NIO (10 microM) blocked ISO- and zinterol-induced increases in [NO](i). ISO-beta(1)-AR stimulation failed to increase [NO](i). Inhibition of G(i)-protein by pertussis toxin significantly inhibited zinterol-mediated increases in [NO](i). Wortmannin (0.2 microM) or LY294002 (10 microM), inhibitors of phosphatidylinositol 3'-kinase (PI-3K), abolished the effects of zinterol to both mediate ACh-activated I(K,ATP) and stimulate [NO](i). We conclude that both beta(1)- and beta(2)-ARs stimulate cAMP. beta(2)-ARs act via two signaling pathways to stimulate cAMP, one of which is mediated via G(i)-protein and PI-3K coupled to NO-cGMP signaling. Only beta(2)-ARs acting exclusively via NO signaling mediate ACh-induced activation of I(K,ATP). NO signaling also contributes to beta(2)-AR stimulation of I(Ca,L). The differential effects of beta(1)- and beta(2)-ARs can be explained by the coupling of these two beta-ARs to different effector signaling pathways.

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Effects of 1 μM zinterol on ICa,L and ACh2-induced K+ conductances in the absence (open bars) and presence (hatched bars) of 10 μM L-NIO (A), an inhibitor of NO synthase, and 10 μM ODQ (B), an inhibitor of soluble guanylate cyclase. L-NIO (A) and ODQ (B) each attenuated zinterol-induced stimulation of ICa,L and abolished the potentiation of ACh2-induced K+ conductances. Ordinates are the same as in Fig. 2.
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Figure 3: Effects of 1 μM zinterol on ICa,L and ACh2-induced K+ conductances in the absence (open bars) and presence (hatched bars) of 10 μM L-NIO (A), an inhibitor of NO synthase, and 10 μM ODQ (B), an inhibitor of soluble guanylate cyclase. L-NIO (A) and ODQ (B) each attenuated zinterol-induced stimulation of ICa,L and abolished the potentiation of ACh2-induced K+ conductances. Ordinates are the same as in Fig. 2.

Mentions: β-AR stimulation can induce NO release in cardiac myocytes (Kanai et al. 1997). Therefore, we sought to determine whether the conditioning effect of β2-AR stimulation is mediated via NO signaling by testing zinterol in the presence of 10 μM L-NIO, an inhibitor of constitutive NO synthase (Rees et al. 1990). The graph in Fig. 3 A shows that in the absence of L-NIO (open bars), zinterol elicited a typical increase in ICa,L (150 ± 21%) and a potentiated increase in ACh2-induced K+ conductance (52 ± 20% at −130 mV, and 40 ± 15% at 30 mV). In a second group of cells from the same hearts, in the presence of L-NIO (Fig. 3 A, hatched bars), zinterol-induced stimulation of ICa,L was attenuated (121 ± 31%), whereas ACh2-induced activation of IK,ATP was abolished (−6 ± 2% at −130 mV, and −7 ± 2% at 30 mV) (n = 12; P < 0.05).


Beta 2-adrenergic receptor signaling acts via NO release to mediate ACh-induced activation of ATP-sensitive K+ current in cat atrial myocytes.

Wang YG, Dedkova EN, Steinberg SF, Blatter LA, Lipsius SL - J. Gen. Physiol. (2002)

Effects of 1 μM zinterol on ICa,L and ACh2-induced K+ conductances in the absence (open bars) and presence (hatched bars) of 10 μM L-NIO (A), an inhibitor of NO synthase, and 10 μM ODQ (B), an inhibitor of soluble guanylate cyclase. L-NIO (A) and ODQ (B) each attenuated zinterol-induced stimulation of ICa,L and abolished the potentiation of ACh2-induced K+ conductances. Ordinates are the same as in Fig. 2.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2233856&req=5

Figure 3: Effects of 1 μM zinterol on ICa,L and ACh2-induced K+ conductances in the absence (open bars) and presence (hatched bars) of 10 μM L-NIO (A), an inhibitor of NO synthase, and 10 μM ODQ (B), an inhibitor of soluble guanylate cyclase. L-NIO (A) and ODQ (B) each attenuated zinterol-induced stimulation of ICa,L and abolished the potentiation of ACh2-induced K+ conductances. Ordinates are the same as in Fig. 2.
Mentions: β-AR stimulation can induce NO release in cardiac myocytes (Kanai et al. 1997). Therefore, we sought to determine whether the conditioning effect of β2-AR stimulation is mediated via NO signaling by testing zinterol in the presence of 10 μM L-NIO, an inhibitor of constitutive NO synthase (Rees et al. 1990). The graph in Fig. 3 A shows that in the absence of L-NIO (open bars), zinterol elicited a typical increase in ICa,L (150 ± 21%) and a potentiated increase in ACh2-induced K+ conductance (52 ± 20% at −130 mV, and 40 ± 15% at 30 mV). In a second group of cells from the same hearts, in the presence of L-NIO (Fig. 3 A, hatched bars), zinterol-induced stimulation of ICa,L was attenuated (121 ± 31%), whereas ACh2-induced activation of IK,ATP was abolished (−6 ± 2% at −130 mV, and −7 ± 2% at 30 mV) (n = 12; P < 0.05).

Bottom Line: Wortmannin (0.2 microM) or LY294002 (10 microM), inhibitors of phosphatidylinositol 3'-kinase (PI-3K), abolished the effects of zinterol to both mediate ACh-activated I(K,ATP) and stimulate [NO](i).We conclude that both beta(1)- and beta(2)-ARs stimulate cAMP. beta(2)-ARs act via two signaling pathways to stimulate cAMP, one of which is mediated via G(i)-protein and PI-3K coupled to NO-cGMP signaling.The differential effects of beta(1)- and beta(2)-ARs can be explained by the coupling of these two beta-ARs to different effector signaling pathways.

View Article: PubMed Central - PubMed

Affiliation: Stritch School of Medicine, Department of Physiology, Loyola University Medical Center, 2160 South First Avenue, Maywood, IL 60153, USA.

ABSTRACT
In atrial myocytes, an initial exposure to isoproterenol (ISO) acts via cAMP to mediate a subsequent acetylcholine (ACh)-induced activation of ATP-sensitive K(+) current (I(K,ATP)). In addition, beta-adrenergic receptor (beta-AR) stimulation activates nitric oxide (NO) release. The present study determined whether the conditioning effect of beta-AR stimulation acts via beta(1)- and/or beta(2)-ARs and whether it is mediated via NO signaling. 0.1 microM ISO plus ICI 118,551 (ISO-beta(1)-AR stimulation) or ISO plus atenolol (ISO-beta(2)-AR stimulation) both increased L-type Ca(2+) current (I(Ca,L)) markedly, but only ISO-beta(2)-AR stimulation mediated ACh-induced activation of I(K,ATP). 1 microM zinterol (beta(2)-AR agonist) also increased I(Ca,L) and mediated ACh-activated I(K,ATP). Inhibition of NO synthase (10 microM L-NIO), guanylate cyclase (10 microM ODQ), or cAMP-PKA (50 microM Rp-cAMPs) attenuated zinterol-induced stimulation of I(Ca,L) and abolished ACh-activated I(K,ATP). Spermine-NO (100 microM; an NO donor) mimicked beta(2)-AR stimulation, and its effects were abolished by Rp-cAMPs. Intracellular dialysis of 20 microM protein kinase inhibitory peptide (PKI) abolished zinterol-induced stimulation of I(Ca,L). Measurements of intracellular NO ([NO](i)) using the fluorescent indicator DAF-2 showed that ISO-beta(2)-AR stimulation or zinterol increased [NO](i). L-NIO (10 microM) blocked ISO- and zinterol-induced increases in [NO](i). ISO-beta(1)-AR stimulation failed to increase [NO](i). Inhibition of G(i)-protein by pertussis toxin significantly inhibited zinterol-mediated increases in [NO](i). Wortmannin (0.2 microM) or LY294002 (10 microM), inhibitors of phosphatidylinositol 3'-kinase (PI-3K), abolished the effects of zinterol to both mediate ACh-activated I(K,ATP) and stimulate [NO](i). We conclude that both beta(1)- and beta(2)-ARs stimulate cAMP. beta(2)-ARs act via two signaling pathways to stimulate cAMP, one of which is mediated via G(i)-protein and PI-3K coupled to NO-cGMP signaling. Only beta(2)-ARs acting exclusively via NO signaling mediate ACh-induced activation of I(K,ATP). NO signaling also contributes to beta(2)-AR stimulation of I(Ca,L). The differential effects of beta(1)- and beta(2)-ARs can be explained by the coupling of these two beta-ARs to different effector signaling pathways.

Show MeSH
Related in: MedlinePlus