Abstract
Abstract
Cardiac ventricular myocytes exhibit a protein kinase A-dependent Cl− current (ICl.PKA) mediated by the cystic fibrosis transmembrane conductance regulator (CFTR). There is conflicting evidence regarding the ability of the divalent cation nickel (Ni2+), which has been used widely in vitro in the study of other cardiac ionic conductances, to inhibit ICl.PKA. Here the action of Ni2+ on ICl.PKA activated by β-adrenergic stimulation has been elucidated. Whole-cell patch-clamp recordings were made from rabbit isolated ventricular myocytes. Externally applied Ni2+ blocked ICl.PKA activated by 1 μM isoprenaline with a log IC50 (M) of −4.107 ± 0.075 (IC50 = 78.1 μM) at +100 mV and −4.322 ± 0.107 (IC50 = 47.6 μM) at −100 mV. Thus, the block of ICl.PKA by Ni2+ was not strongly voltage dependent. Ni2+ applied internally via the patch-pipette was ineffective at inhibiting isoprenaline-activated ICl,PKA, but in the same experiments the current was suppressed by external Ni2+ application, indicative of an external site of Ni2+ action. In the presence of 1 μM atenolol isoprenaline was ineffective at activating ICl.PKA, but in the presence of the β2-adrenoceptor inhibitor ICI 118,551 isoprenaline still activated Ni2+-sensitive ICl.PKA. Collectively, these data demonstrate that Ni2+ ions produce marked inhibition of β1-adrenoceptor activated ventricular ICl.PKA at submillimolar [Ni2+]: an action that is likely to involve an interaction between Ni2+ and β1-adrenoceptors. The concentration-dependence for ICl.PKA inhibition seen here indicates the potential for confounding effects on ICl,PKA to occur even at comparatively low Ni2+ concentrations, when Ni2+ is used to study other cardiac ionic currents under conditions of β-adrenergic agonism.
Cardiac ventricular myocytes exhibit a protein kinase A-dependent Cl− current (ICl.PKA) mediated by the cystic fibrosis transmembrane conductance regulator (CFTR). There is conflicting evidence regarding the ability of the divalent cation nickel (Ni2+), which has been used widely in vitro in the study of other cardiac ionic conductances, to inhibit ICl.PKA. Here the action of Ni2+ on ICl.PKA activated by β-adrenergic stimulation has been elucidated. Whole-cell patch-clamp recordings were made from rabbit isolated ventricular myocytes. Externally applied Ni2+ blocked ICl.PKA activated by 1 μM isoprenaline with a log IC50 (M) of −4.107 ± 0.075 (IC50 = 78.1 μM) at +100 mV and −4.322 ± 0.107 (IC50 = 47.6 μM) at −100 mV. Thus, the block of ICl.PKA by Ni2+ was not strongly voltage dependent. Ni2+ applied internally via the patch-pipette was ineffective at inhibiting isoprenaline-activated ICl,PKA, but in the same experiments the current was suppressed by external Ni2+ application, indicative of an external site of Ni2+ action. In the presence of 1 μM atenolol isoprenaline was ineffective at activating ICl.PKA, but in the presence of the β2-adrenoceptor inhibitor ICI 118,551 isoprenaline still activated Ni2+-sensitive ICl.PKA. Collectively, these data demonstrate that Ni2+ ions produce marked inhibition of β1-adrenoceptor activated ventricular ICl.PKA at submillimolar [Ni2+]: an action that is likely to involve an interaction between Ni2+ and β1-adrenoceptors. The concentration-dependence for ICl.PKA inhibition seen here indicates the potential for confounding effects on ICl,PKA to occur even at comparatively low Ni2+ concentrations, when Ni2+ is used to study other cardiac ionic currents under conditions of β-adrenergic agonism.
| Original language | Undefined |
|---|---|
| Journal | Biochemical and Biophysical Research Communications |
| DOIs | |
| Publication status | Published - 2013 |
