Simultaneous measurement of Ca2+, contraction, and potential in cardiac myocytes

Spurgeon, Harold A.; Stern, Michael D.; Baartz, G.; Raffaeli, S.; Hansford, Richard G.; Talo, A; Lakatta, Edward G.; Capogrossi, M. C.

doi:10.1152/ajpheart.1990.258.2.h574

Cited by 145 publications

(161 citation statements)

References 0 publications

Supporting

Mentioning

156

Contrasting

Order By: Relevance

“…Separately, isolated cells were loaded with 25 M Indo-1 AM and 1% pluronic acid (Molecular Probes) for 10 min at room temperature. Calcium transients were measured with external pacing at room temperature as described (22).…”

Section: Herpes Simplex Virus (Hsv)-1 Amplicon-mediated Rescuementioning

confidence: 99%

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

Huang

Tweedie

Wang

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

108

View full text Add to dashboard Cite

In adult myocardium, the heartbeat originates from the sequential activation of ionic currents in pacemaker cells of the sinoatrial node. Ca 2؉ release via the ryanodine receptor (RyR) modulates the rate at which these cells beat. In contrast, the mechanisms that regulate heart rate during early cardiac development are poorly understood. Embryonic stem (ES) cells can differentiate into spontaneously contracting myocytes whose beating rate increases with differentiation time. These cells thus offer an opportunity to determine the mechanisms that regulate heart rate during development. Here we show that the increase in heart rate with differentiation is markedly depressed in ES cell-derived cardiomyocytes with a functional knockout (KO) of the cardiac ryanodine receptor (RyR2). KO myocytes show a slowing of the rate of spontaneous diastolic depolarization and an absence of calcium sparks. The depressed rate of pacemaker potential can be mimicked in wild-type myocytes by ryanodine, and rescued in KO myocytes with herpes simplex virus (HSV)-1 amplicons containing full-length RyR2. We conclude that a functional RyR2 is crucial to the progressive increase in heart rate during differentiation of ES cell-derived cardiomyocytes, consistent with a mechanism that couples Ca 2؉ release via RyR before an action potential with activation of an inward current that accelerates membrane depolarization.

show abstract

Section: Herpes Simplex Virus (Hsv)-1 Amplicon-mediated Rescuementioning

confidence: 99%

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

Huang

Tweedie

Wang

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

108

View full text Add to dashboard Cite

show abstract

“…16 The cells were suspended in HEPES buffer (pH 7.4) containing (mmol/L) HEPES 20, CaCl 2 1, NaCl 137, KCl 5, dextrose 15, MgSO 4 1.3, and NaH 2 PO 4 1.2. Cell length was monitored from the bright-field image by an optical edge-tracking method using a photodiode array (model 1024 SAQ, Reticon) with a 3-ms time resolution.…”

Section: Electrophysiological and Contractile Measurements In Isolatementioning

confidence: 99%

“…Cell length was monitored from the bright-field image by an optical edge-tracking method using a photodiode array (model 1024 SAQ, Reticon) with a 3-ms time resolution. 16 I Ca was measured via the whole-cell patch-clamp technique using an Axopatch 1D amplifier (Axon Instruments Inc). 1 Cells were voltage-clamped at Ϫ40 mV to inactivate Na ϩ and T-type Ca 2ϩ channels.…”

Section: Electrophysiological and Contractile Measurements In Isolatementioning

confidence: 99%

β ₂ -Adrenergic cAMP Signaling Is Uncoupled From Phosphorylation of Cytoplasmic Proteins in Canine Heart

et al. 1999

View full text Add to dashboard Cite

Background —Recent studies of β-adrenergic receptor (β-AR) subtype signaling in in vitro preparations have raised doubts as to whether the cAMP/protein kinase A (PKA) signaling is activated in the same manner in response to β 2 -AR versus β 1 -AR stimulation. Methods and Results —The present study compared, in the intact dog, the magnitude and characteristics of chronotropic, inotropic, and lusitropic effects of cAMP accumulation, PKA activation, and PKA-dependent phosphorylation of key effector proteins in response to β-AR subtype stimulation. In addition, many of these parameters and L-type Ca 2+ current ( I Ca ) were also measured in single canine ventricular myocytes. The results indicate that although the cAMP/PKA-dependent phosphorylation cascade activated by β 1 -AR stimulation could explain the resultant modulation of cardiac function, substantial β 2 -AR–mediated chronotropic, inotropic, and lusitropic responses occurred in the absence of PKA activation and phosphorylation of nonsarcolemmal proteins, including phospholamban, troponin I, C protein, and glycogen phosphorylase kinase. However, in single canine myocytes, we found that β 2 -AR–stimulated increases in both I Ca and contraction were abolished by PKA inhibition. Thus, the β 2 -AR–directed cAMP/PKA signaling modulates sarcolemmal L-type Ca 2+ channels but does not regulate PKA-dependent phosphorylation of cytoplasmic proteins. Conclusions —These results indicate that the dissociation of β 2 -AR signaling from cAMP regulatory systems is only apparent and that β 2 -AR–stimulated cAMP/PKA signaling is uncoupled from phosphorylation of nonsarcolemmal regulatory proteins involved in excitation-contraction coupling.

show abstract

“…he ␤-adrenergic agonists are known to potentiate the force of cardiac contraction by enhancing Ca 2ϩ current (I Ca ) and Ca 2ϩ release from the internal calcium store secondary to cAMP-dependent phosphorylation of the Ca 2ϩ channel (1)(2)(3). Relaxant effect of catecholamines (4), on the other hand, appears to be mediated by phosphorylation of phospholamban and troponin C resulting in stimulation of the Ca 2ϩ pump (5,6) and decreased myofilament Ca 2ϩ sensitivity (7)(8)(9).…”

mentioning

confidence: 99%

Bimodal regulation of Na+-Ca2+ exchanger by beta -adrenergic signaling pathway in shark ventricular myocytes

Woo

Morad²

2001

Proceedings of the National Academy of Sciences

View full text Add to dashboard Cite

In shark heart, the Na ؉ -Ca 2؉ exchanger serves as a major pathway for both Ca 2؉ influx and efflux, as there is only rudimentary sarcoplasmic reticulum in these hearts. The modulation of the exchanger by a ␤-adrenergic agonist in whole-cell clamped ventricular myocytes was compared with that of the Na ؉ -Ca 2؉ exchanger blocker KB-R7943. Application of 5 M isoproterenol and 10 M KB-R7943 suppressed both the inward and the outward Na ؉ -Ca 2؉ exchanger current (I Na؊Ca ). The isoproterenol effect was mimicked by 10 M forskolin. Isoproterenol and forskolin shifted the reversal potential (Erev) of INa؊Ca by approximately ؊23 mV and ؊30 mV, respectively. An equivalent suppression of outward I Na؊Ca by KB-R7943 to that by isoproterenol produced a significantly smaller shift in Erev of about ؊4 mV. The ratio of inward to outward exchanger currents was also significantly larger in isoproterenolthan in control-and KB-R7943-treated myocytes. Our data suggest that the larger ratio of inward to outward exchanger currents as well as the larger shift in Erev with isoproterenol results from the enhanced efficacy of Ca 2؉ efflux via the exchanger. The protein kinase A-mediated bimodal regulation of the exchanger in parallel with phosphorylation of the Ca 2؉ channel and enhancement of its current may have evolved to satisfy the evolutionary needs for accelerated contraction and relaxation in hearts of animals with vestigial sarcoplasmic Ca 2؉ release stores. The ␤-adrenergic agonists are known to potentiate the force of cardiac contraction by enhancing Ca 2ϩ current (I Ca ) and Ca 2ϩ release from the internal calcium store secondary to cAMP-dependent phosphorylation of the Ca 2ϩ channel (1-3). Relaxant effect of catecholamines (4), on the other hand, appears to be mediated by phosphorylation of phospholamban and troponin C resulting in stimulation of the Ca 2ϩ pump (5, 6) and decreased myofilament Ca 2ϩ sensitivity (7-9). Similar to the mammalian myocardium, the shark heart also exhibits some of the features associated with ␤-agonist response, namely enhancement of I Ca (10) and twitch force, and suppression of maintained contracture tension (11). In light of previous reports showing little ultrastructural and functional evidence for Ca 2ϩ release stores in shark heart (12, 13), the ␤-adrenergic-induced suppression of KCl-induced contractures (11) may be somewhat surprising. In shark heart the Na ϩ -Ca 2ϩ exchanger appears to serve as a major pathway of both Ca 2ϩ influx and efflux (13). Here we report on a cellular mechanism by which the ␤-adrenergic agonists suppress the influx and efflux mode of the Na ϩ -Ca 2ϩ exchanger, but enhance the efficacy of Ca 2ϩ efflux (I inward ͞I outward ) via the exchanger. To gain insight into the mechanism by which isoproterenol regulates the Na ϩ -Ca 2ϩ exchanger, we compared the effects of this hormone with that of the exchanger blocker . Our experiments reveal that in shark myocytes this bimodal regulation of the exchanger may decrease the Ca 2ϩ load of the myocytes during experimentally ...

show abstract

Simultaneous measurement of Ca2+, contraction, and potential in cardiac myocytes

Cited by 145 publications

References 0 publications

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

β ₂ -Adrenergic cAMP Signaling Is Uncoupled From Phosphorylation of Cytoplasmic Proteins in Canine Heart

Bimodal regulation of Na+-Ca2+ exchanger by beta -adrenergic signaling pathway in shark ventricular myocytes

Contact Info

Product

Resources

About

Simultaneous measurement of Ca2+, contraction, and potential in cardiac myocytes

Cited by 145 publications

References 0 publications

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development

β 2 -Adrenergic cAMP Signaling Is Uncoupled From Phosphorylation of Cytoplasmic Proteins in Canine Heart

Bimodal regulation of Na+-Ca2+ exchanger by beta -adrenergic signaling pathway in shark ventricular myocytes

Contact Info

Product

Resources

About

β ₂ -Adrenergic cAMP Signaling Is Uncoupled From Phosphorylation of Cytoplasmic Proteins in Canine Heart