Calcium current in single cells isolated from normal and hypertrophied rat heart. Effects of beta-adrenergic stimulation.

Scamps, Frédérique; Mayoux, Eric; Charlemagne, D.; Vassort, Guy

doi:10.1161/01.res.67.1.199

Cited by 128 publications

(78 citation statements)

References 37 publications

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“…The E max of isoproterenol obtained for sham myocytes was similar to values previously reported for adult rat hearts (36), while the present study is the first report of E max and EC 50 in postinfarction rat myocytes. The maintenance of EC 50 and the decrease in E max in postinfarction myocytes suggest that the reduced effect of isoproterenol on these cells is more likely to be related to a decreased ß-adrenergic receptor density rather than to a change in affinity of the ß-adrenergic receptor.…”

Section: Depressed ß-Adrenergic Response In Postinfarction Myocytessupporting

confidence: 91%

Impaired beta-adrenergic response and decreased L-type calcium current of hypertrophied left ventricular myocytes in postinfarction heart failure

Saraiva

Chedid

Masuda

2003

Braz J Med Biol Res

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Infarct-induced heart failure is usually associated with cardiac hypertrophy and decreased ß-adrenergic responsiveness. However, conflicting results have been reported concerning the density of L-type calcium current (I Ca(L) ), and the mechanisms underlying the decreased ß-adrenergic inotropic response. We determined I Ca(L) density, cytoplasmic calcium ([Ca 2+ ] i ) transients, and the effects of ß-adrenergic stimulation (isoproterenol) in a model of postinfarction heart failure in rats. Left ventricular myocytes were obtained by enzymatic digestion 8-10 weeks after infarction. Electrophysiological recordings were obtained using the patch-clamp technique. [Ca 2+ ] i transients were investigated via fura-2 fluorescence. ß-Adrenergic receptor density was determined by [ 3 H]-dihydroalprenolol binding to left ventricle homogenates. Postinfarction myocytes showed a significant 25% reduction in mean I Ca(L) density (5.7 ± 0.28 vs 7.6 ± 0.32 pA/pF) and a 19% reduction in mean peak [Ca 2+ ] i transients (0.13 ± 0.007 vs 0.16 ± 0.009) compared to sham myocytes. The isoproterenol-stimulated increase in I Ca(L) was significantly smaller in postinfarction myocytes (E max : 63.6 ± 4.3 vs 123.3 ± 0.9% in sham myocytes), but EC 50 was not altered. The isoproterenol-stimulated peak amplitude of [Ca 2+ ] i transients was also blunted in postinfarction myocytes. Adenylate cyclase activation through forskolin produced similar I Ca(L) increases in both groups. ß-Adrenergic receptor density was significantly reduced in homogenates from infarcted hearts (B max : 93.89 ± 20.22 vs 271.5 ± 31.43 fmol/mg protein in sham myocytes), while Kd values were similar. We conclude that postinfarction myocytes from large infarcts display reduced I Ca(L) density and peak [Ca 2+ ] i transients. The response to ß-adrenergic stimulation was also reduced and was probably related to ß-adrenergic receptor down-regulation and not to changes in adenylate cyclase activity.

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Section: Depressed ß-Adrenergic Response In Postinfarction Myocytessupporting

confidence: 91%

Impaired beta-adrenergic response and decreased L-type calcium current of hypertrophied left ventricular myocytes in postinfarction heart failure

Saraiva

Chedid

Masuda

2003

Braz J Med Biol Res

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“…Male Wistar rats (180-250 g) were anesthetized by intraperitoneal injection of urethane (2 g/kg) and heparin (2.5 mg/kg). Ventricular cardiomyocytes were dispersed using collagenase A (0.255 mg/ml; Boehringer-Mannheim Biochemica, Mannheim, Germany) as previously described (31). At the end of the retrograde perfusion, atria and ventricles were separated, and the isolated ventricular myocytes were resuspended, step by step, in a 1 mM Ca 2ϩ -containing solution.…”

Section: Methodsmentioning

confidence: 99%

Methylene Blue Is a Muscarinic Antagonist in Cardiac Myocytes

et al. 1997

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SUMMARYWe studied the mechanism of action of methylene blue (Mblue), a putative guanylyl cyclase inhibitor, on the L-type calcium current (I Ca ) and the muscarinic activated K ϩ current (I K,ACh ) in rat ventricular and atrial myocytes, respectively, and on the binding of [3 H]quinuclidinyl benzylate in rat ventricular membranes. Superfusion, but not internal dialysis, with 30 M Mblue antagonized the inhibitory effect of acetylcholine (ACh, 1 M) on ␤-adrenergic stimulation of I Ca with isoprenaline (Iso, 10 nM or 1 M). However, Mblue had no effect on the basal I Ca or on the stimulation of I Ca by Iso in the absence of ACh. The activation of I K,ACh by 3 M ACh was also antagonized by Mblue in a dose-dependent manner. In contrast, Mblue had no effect on the activation of I K,ACh by either guanosine-5Ј-O-(3-thio)-triphosphate or guanosine-5Ј-(␤,␥-imido)triphosphate. Chlorpromazine (CPZ), a piperazine derivative like Mblue, also inhibited the muscarinic activation of I K,ACh in a dose-dependent manner. The specific binding of [ 3 H]QNB, a muscarinic ligand, to rat ventricular membranes was displaced in a dose-dependent manner by Mblue and CPZ. The piperazine derivatives behaved like competitive antagonists of [ 3 H]QNB binding, exhibiting equilibrium dissociation constant (K i ) values of 187 nM for Mblue and 366 nM for CPZ. In conclusion, Mblue exerts antimuscarinic effects on I Ca and I K,ACh in rat cardiac myocytes that are best explained by the binding of Mblue to the M2 subtype of muscarinic receptors. This property probably contributes to the antimuscarinic effect of the putative guanylyl cyclase inhibitor reported in previous studies.Mblue has been shown to antagonize the production of cGMP in various tissues and is generally accepted as a selective antagonist of the NO-sensitive isoform of guanylyl cyclase (1-5). As such, Mblue is often used to study the roles of NO and cGMP in the effects of neurotransmitters and hormones. For instance, Mblue antagonizes the effect of ACh on the relaxation of coronary vessels (6, 7).In the heart, Mblue was soon recognized as an inhibitor of the response to ACh (Ref. 8 and references therein). Because ACh, like NO donors, can increase cGMP levels in cardiac myocytes (for reviews, see Refs. 9 and 10), a likely mechanism for the cardiac effect of Mblue was the inhibition of guanylyl cyclase. Consistent with this hypothesis are the recent findings that Mblue (i) inhibits cGMP production induced by ACh in isolated guinea pig cardiomyocytes (11), (ii) prevents the inhibitory effect of ACh on the L-type Ca 2ϩ channel current (I Ca ) (12-15), (iii) prevents the inhibitory effect of ACh on the cAMP-stimulated Cl Ϫ current (16), and (iv) antagonizes the effects of NO donors on cardiac contractility (17, 18) and I Ca (12,14,19 Previous studies have questioned the mechanism of action of Mblue and suggested that Mblue is not a direct guanylyl cyclase inhibitor. Indeed, Mblue is a superoxide anion generator, and this anion, which is a potent NO scavenger, may

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“…Previous studies on left ventricular trabeculae (Meszaros & Levai, 1990, 1992Meszaros, 1992) (Kleiman & Houser, 1988;Scamps et al 1990;Bouron, Potreau & Raymond, 1992;Cerbai, Barbieri, Li & Mugelli, 1994) although in mild (Ryder et al 1993) and moderate (Keung, 1989) hypertrophy, an increase in ICa density has been reported. Only in severe cardiac hypertrophy, in which congestion is present, has ICa density been reported to decrease (Nuss & Houser, 1991; Rossner, 1991;Aiba & Creazzo, 1992;Hatem, Sham & Morad, 1994; LeGrand, Hatem, Deroubaix, Couetil & Coraboeuf, 1994;Ming, Nordin, Sirn & Aronson, 1994).…”

Section: Discussionmentioning

confidence: 84%

L‐type calcium current in catecholamine‐induced cardiac hypertrophy in the rat

Meszaros

Coutinho²,

Bryant³

et al. 1997

Experimental Physiology

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SUMMARYThis study investigates whether an increase in L-type calcium current (Ica) could explain the prolongation of the action potential associated with the cardiac hypertrophy produced by repeated administration of isoprenaline. Hypertrophy was induced by daily injection of isoprenaline (5 mg/kg i.p.) for 7 days in male Wistar rats. Under whole-cell voltage-clamp conditions, ICa was evoked in Na+-and Kt-free solution, by step depolarizations from a holding potential of -45 mV in single left ventricular myocytes isolated from control and hypertrophied rat hearts. In the test group, heart weight to body weight ratio and cell membrane capacitance were increased by 30 and 34%, respectively. Peak 'Ca was increased by 26 % (control, -1 46 + 0.06 nA, n = 17; hypertrophy, -1 85 + 0.13 nA, n = 19; P < 0.02). However, when normalized for cell capacitance, there was no significant difference in peak current density (control, -12 1 + 0-5 pA/pF; hypertrophy, -11-5 + 0 6 pA/pF). The voltage dependence of ICa was similar in both cell types. No change was observed either in the steady-state activation or inactivation kinetics, or in the time course of inactivation. The recovery from inactivation of ICa' when fitted with a monoexponential function with time constant Trec was not changed significantly by hypertrophy (control, Tree = 115 + 23 ms, n = 9; hypertrophy, Trec = 120 + 12 ms, n = 15). The increased calcium current occurs in parallel with the increase in cell size. The prolonged action potential duration seen in this model must be explained by changes in currents other than L-type calcium current.

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Calcium current in single cells isolated from normal and hypertrophied rat heart. Effects of beta-adrenergic stimulation.

Cited by 128 publications

References 37 publications

Impaired beta-adrenergic response and decreased L-type calcium current of hypertrophied left ventricular myocytes in postinfarction heart failure

Impaired beta-adrenergic response and decreased L-type calcium current of hypertrophied left ventricular myocytes in postinfarction heart failure

Methylene Blue Is a Muscarinic Antagonist in Cardiac Myocytes

L‐type calcium current in catecholamine‐induced cardiac hypertrophy in the rat

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