Intracellular calcium handling heterogeneities in intact guinea pig hearts

2004 ◽  
Vol 286 (2) ◽  
pp. H648-H656 ◽  
Author(s):  
Rodolphe P. Katra ◽  
Etienne Pruvot ◽  
Kenneth R. Laurita
Keyword(s):  
Guinea Pig ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Optical Mapping ◽  
Contractile Function ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Calcium Handling ◽  
Excitation Light ◽  
Intact Heart

Regional heterogeneities of ventricular repolarizing currents and their role in arrhythmogenesis have received much attention; however, relatively little is known regarding heterogeneities of intracellular calcium handling. Because repolarization properties and contractile function are heterogeneous from base to apex of the intact heart, we hypothesize that calcium handling is also heterogeneous from base to apex. To test this hypothesis, we developed a novel ratiometric optical mapping system capable of measuring calcium fluorescence of indo-1 at two separate wavelengths from 256 sites simultaneously. With the use of intact Langendorff-perfused guinea pig hearts, ratiometric calcium transients were recorded under normal conditions and during administration of known inotropic agents. Ratiometric calcium transients were insensitive to changes in excitation light intensity and fluorescence over time. Under control conditions, calcium transient amplitude near the apex was significantly larger (60%, P < 0.01) compared with the base. In contrast, calcium transient duration was significantly longer (7.5%, P < 0.03) near the base compared with the apex. During isoproterenol (0.05 μM) and verapamil (2.5 μM) administration, ratiometric calcium transients accurately reflected changes in contractile function, and, the direction of base-to-apex heterogeneities remained unchanged compared with control. Ratiometric optical mapping techniques can be used to accurately quantify heterogeneities of calcium handling in the intact heart. Significant heterogeneities of calcium release and sequestration exist from base to apex of the intact heart. These heterogeneities are consistent with base-to-apex heterogeneities of contraction observed in the intact heart and may play a role in arrhythmogenesis under abnormal conditions.

Caffeine attenuates contraction-induced diminutions of the intracellular calcium transient in mouse lumbrical muscle ex vivo

2019 ◽  
Vol 97 (5) ◽  
pp. 429-435 ◽  
Author(s):  
Ian C. Smith ◽  
Rene Vandenboom ◽  
A. Russell Tupling
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Ex Vivo ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Inotropic Effects ◽  
Intracellular Calcium Transient ◽  
Lumbrical Muscle ◽  
Lumbrical Muscles

The amount of calcium released from the sarcoplasmic reticulum in skeletal muscle rapidly declines during repeated twitch contractions. In this study, we test the hypothesis that caffeine can mitigate these contraction-induced declines in calcium release. Lumbrical muscles were isolated from male C57BL/6 mice and loaded with the calcium-sensitive indicator, AM-furaptra. Muscles were then stimulated at 8 Hz for 2.0 s in the presence or absence of 0.5 mM caffeine, at either 30 °C or 37 °C. The amplitude and area of the furaptra-based intracellular calcium transients and force produced during twitch contractions were calculated. For each of these measures, the values for twitch 16 relative to twitch 1 were higher in the presence of caffeine than in the absence of caffeine at both temperatures. We conclude that caffeine can attenuate contraction-induced diminutions of calcium release during repeated twitch contractions, thereby contributing to the inotropic effects of caffeine.

Mapping action potentials and calcium transients simultaneously from the intact heart

2001 ◽  
Vol 280 (5) ◽  
pp. H2053-H2060 ◽  
Author(s):  
Kenneth R. Laurita ◽  
Ashish Singal
Keyword(s):  
Action Potentials ◽  
Cardiac Electrophysiology ◽  
Optical Mapping ◽  
Fluorescence Emission ◽  
Calcium Transients ◽  
Calcium Handling ◽  
Guinea Pig Heart ◽  
Spectral Overlap ◽  
Intact Heart

Intracellular calcium handling plays an important role in cardiac electrophysiology. Using two fluorescent indicators, we developed an optical mapping system that is capable of measuring calcium transients and action potentials at 256 recording sites simultaneously from the intact guinea pig heart. On the basis of in vitro measurements of dye excitation and emission spectra, excitation and emission filters at 515 ± 5 and >695 nm, respectively, were used to measure action potentials with di-4-ANEPPS, and excitation and emission filters at 365 ± 25 and 485 ± 5 nm, respectively, were used to measure calcium transients with indo 1. The percent error due to spectral overlap was small when action potentials were measured (1.7 ± 1.0%, n = 3) and negligible when calcium transients were measured (0%, n = 3). Recordings of calcium transients, action potentials, and isochrone maps of depolarization time and the time of calcium transient onset indicated negligible error due to fluorescence emission overlap. These data demonstrate that the error due to spectral overlap of indo 1 and di-4-ANEPPS is sufficiently small, such that optical mapping techniques can be used to measure calcium transients and action potentials simultaneously in the intact heart.

Abstract MP135: Cardiac Sarcoplasmic Reticulum Calcium Cycling is Regulated by Kinase Independent Function of Pi3kgamma

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Maradumane L Mohan ◽  
Conner P Witherow ◽  
Robert S Papay ◽  
Sathyamangla V Naga Prasad
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Cardiac Contractility ◽  
Underlying Mechanism ◽  
Calcium Handling ◽  
Ventricular Contractility ◽  
Independent Function ◽  
Calcium Cycling ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Phosphoinositide 3 Kinase

Genetic deletion of Phosphoinositide 3-kinase (PI3Kγ) in mice (PI3Kγ -/- ) results in increased cAMP levels and enhanced ventricular contractility. We investigated whether the lack of PI3Kγ plays a role in cardiac contractility by altering intracellular calcium recycling. Isolated cardiomyocytes from PI3Kγ -/- mice showed significantly reduced calcium reuptake by sarcoendoplasmic reticulum (SR) following caffeine induced calcium release indicating that PI3Kγ locally regulates the function of SR. The intracellular calcium remained at elevated levels in the cardiomyocytes of PI3Kγ -/- for a prolonged period after caffeine treatment. This could be due to changes in phosphorylation of SERCA2, Ryanodine receptor (RyR 2 ) or phospholamban (PLN). In fact, when we looked at phosphorylation of PLN in cardiac lysates, a major regulator of cardiac contractility and relaxation, PI3Kγ -/- mice showed significantly reduced PLN phosphorylation compared to littermate controls. Previous studies from our laboratory suggested that absence of PI3Kγ leads to increase in protein phosphatase (PP) activity which could be possible reason for rapid dephosphorylation of PLN, resulting in inhibition of SERCA2 pump. We observed increased SR associated PP activity and PLN associated PP activity in PI3Kγ -/- mice. We also observed increased association of PP-1 and PP2A with PLN in the absence of PI3Kγ. The altered calcium handling in the cardiomyocytes of PI3Kγ -/- mice could be restored to the level of WT controls by okadaic acid mediated inhibition of PP, suggesting that PI3Kγ plays a role in regulating PP activity associated with SR. To test whether PI3Kγ activity is required for PLN dephosphorylation and SR calcium cycling, we used mice with cardiac specific overexpression of kinase dead PI3Kγ (PI3Kγ inact ) in global PI3Kγ -/- mice (PI3Kγ inact /PI3Kγ -/- ). PI3Kγ inact /PI3Kγ -/- mice showed restored PLN phosphorylation, improved caffeine induced calcium reuptake, decreased SR and PLN associated PP activity. These studies show a novel regulation of PP and SR calcium regulation by kinase independent function of PI3Kγ. The underlying mechanism of PP regulation by PI3Kγ will be presented.

Taurocholate induces changes in rat cardiomyocyte contraction and calcium dynamics

2002 ◽  
Vol 103 (2) ◽  
pp. 191-200 ◽  
Author(s):  
Julia GORELIK ◽  
Sian E. HARDING ◽  
Andrew I. SHEVCHUK ◽  
Duleepa KORALAGE ◽  
Max LAB ◽  
...  
Keyword(s):  
Bile Acid ◽  
Calcium Release ◽  
Contractile Function ◽  
Calcium Transient ◽  
Intrauterine Death ◽  
Ion Conductance ◽  
Rat Cardiomyocytes ◽  
Contraction Amplitude ◽  
Neonatal Cardiomyocytes ◽  
Reduced Rate

Obstetric cholestasis is characterized by raised bile acids, and can be complicated by intrauterine death. We have shown that the bile acid taurocholate causes loss of synchronous beating, bradycardia and cessation of contraction in cultured rat cardiomyocytes [Williamson, Gorelik, Eaton, Lab, de Swiet and Korchev (2001) Clin. Sci. 100, 363–369]. The aim of the present study was to investigate the effect of taurocholate on cardiomyocytes further. We demonstrated a reduced rate of contraction and proportion of beating cells when rat cardiomyocytes were exposed to increasing concentrations of taurocholate (0.1–3.0mM); more marked at higher concentrations (P<0.001). Using scanning ion-conductance microscopy, we also demonstrated reduced amplitude of contraction and calcium transients with taurocholate. Our observations indicate that taurocholate affects calcium release from the sarcoplasmic reticulum and this parallels changes in contractile function. The relationship between the contraction amplitude and calcium transient is not linear, particularly at higher concentrations of taurocholate. We observed different effects in individual cultured neonatal cells; a reversible reduction in rate and amplitude of contraction in some, and irreversible oscillatory (fibrillatory) cessation of beating in others. The effects were more marked with higher concentrations. The contraction amplitude was also reduced in adult cardiomyocytes. The changes were reversible following removal of taurocholate in adult, but not in neonatal, cardiomyocytes exposed to higher concentrations (>0.3mM) (P<0.001). In conclusion we have demonstrated that the bile acid taurocholate can cause different types of dysrhythmia in individual cardiomyocytes. These results provide further support for the hypothesis that obstetric cholestasis may produce cardiac-related sudden intrauterine death.

Meiosis-associated calcium waves in ascidian oocytes are correlated with the position of the male centrosome

Zygote ◽  
2000 ◽  
Vol 8 (4) ◽  
pp. 285-293 ◽  
Author(s):  
Martin Wilding ◽  
Marcella Marino ◽  
Vincenzo Monfrecola ◽  
Brian Dale
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Polar Body ◽  
Calcium Transients ◽  
Calcium Waves ◽  
Oocyte Activation ◽  
Animal Pole ◽  
Vegetal Pole ◽  
Sperm Penetration ◽  
Oocyte Cytoplasm

We have used confocal microscopy to measure calcium waves and examine the distribution of tubulin in oocytes of the ascidian Ciona intestinalis during meiosis. We show that the fertilisation calcium wave in these oocytes originates in the vegetal pole. The sperm penetration site and female meiotic apparatus are found at opposite poles of the oocyte at fertilisation, confirming that C. intestinalis sperm enter in the vegetal pole of the oocyte. Following fertilisation, ascidian oocytes are characterised by repetitive calcium waves. Meiosis I-associated waves originate at the vegetal pole of the oocyte, and travel towards the animal pole. In contrast, the calcium waves during meiosis II initiate at the oocyte equator, and cross the oocyte cytoplasm perpendicular to the point of emission of the polar body. Immunolocalisation of tubulin during meiosis II reveals that the male centrosome is also located between animal and vegetal poles prior to initiation of the meiosis II-associated calcium waves, suggesting that the male centrosome influences the origin of these calcium transients. Ascidians are also characterised by an increase in sensitivity to intracellular calcium release after fertilisation. We show that this is not simply an effect of oocyte activation. The data strongly suggest a role for the male centrosome in controlling the mechanism and localisation of post-fertilisation intracellular calcium waves.

scholarly journals Air bubble contact with endothelial cells in vitro induces calcium influx and IP3-dependent release of calcium stores

2011 ◽  
Vol 301 (3) ◽  
pp. C679-C686 ◽  
Author(s):  
Peter Sobolewski ◽  
Judith Kandel ◽  
Alexandra L. Klinger ◽  
David M. Eckmann
Keyword(s):  
Endothelial Cells ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Transient Receptor Potential ◽  
Calcium Influx ◽  
Calcium Transient ◽  
Epifluorescence Microscopy ◽  
Transient Receptor Potential Vanilloid ◽  
Calcium Stores ◽  
Air Bubble

Gas embolism is a serious complication of decompression events and clinical procedures, but the mechanism of resulting injury remains unclear. Previous work has demonstrated that contact between air microbubbles and endothelial cells causes a rapid intracellular calcium transient and can lead to cell death. Here we examined the mechanism responsible for the calcium rise. Single air microbubbles (50–150 μm), trapped at the tip of a micropipette, were micromanipulated into contact with individual human umbilical vein endothelial cells (HUVECs) loaded with Fluo-4 (a fluorescent calcium indicator). Changes in intracellular calcium were then recorded via epifluorescence microscopy. First, we confirmed that HUVECs rapidly respond to air bubble contact with a calcium transient. Next, we examined the involvement of extracellular calcium influx by conducting experiments in low calcium buffer, which markedly attenuated the response, or by pretreating cells with stretch-activated channel blockers (gadolinium chloride or ruthenium red), which abolished the response. Finally, we tested the role of intracellular calcium release by pretreating cells with an inositol 1,4,5-trisphosphate (IP3) receptor blocker (xestospongin C) or phospholipase C inhibitor (neomycin sulfate), which eliminated the response in 64% and 67% of cases, respectively. Collectively, our results lead us to conclude that air bubble contact with endothelial cells causes an influx of calcium through a stretch-activated channel, such as a transient receptor potential vanilloid family member, triggering the release of calcium from intracellular stores via the IP3 pathway.

Cardiac excitation–contraction coupling: new developments

1988 ◽  
Vol 66 (9) ◽  
pp. 1217-1217
Author(s):  
D. Bose
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Myocardial Cell ◽  
Cardiac Contraction ◽  
Calcium Handling ◽  
Patch Clamp Technique ◽  
Regulatory Processes ◽  
Technological Advances ◽  
Calcium Indicator ◽  
Cardiac Excitation

Over 100 years have elapsed since Sidney Ringer made the serendipitous discovery that calcium played a crucial role in amphibian cardiac contraction. Since then we have learned that this ion is an obligatory requirement for cardiac muscle of all species, and that the regulation of intracellular calcium levels is considerably more complex in the mammalian heart than previously thought. Part of this complexity is due to the involved design requirements of mammalian physiological processes. Another element of complexity is introduced by the quantitative differences in the involvement of various regulatory processes in different species. Finally, many significant technological advances in methods for investigating cardiac cellular functions have provided exciting experimental data. However, these data must be integrated into a unifying framework of knowledge of cardiac functions. Among the exciting recent developments are the use of a patch clamp technique to discover different kinds of calcium channels, a highly refined skinned fiber technique to study calcium-induced calcium release, and calcium indicator dyes and laser diffraction and scattering techniques to study the dynamics of calcium handling by the cell. These studies have not only provided clues about the normal functioning of the myocardial cell but have also reinforced the notion that altered function of the sarcoplasmic reticulum during intracellular calcium overload can influence sarcolemmal electrical function.This symposium, organized by the Pharmacological Society of Canada, examined some of the more recent technological advances in the field to provide a glimpse not only of the "state of the art" but also of future directions.This symposium was made possible by generous financial assistance from Boehringer Ingelheim (Canada) Ltd., Bristol-Myers Pharmaceutical Group, Canadian and Manitoba Heart Foundations, Ciba-Geigy Canada Ltd., Du Pont Canada Inc., Hoffmann LaRoche Ltd., Merck-Frosst Canada Inc., Miles Laboratories Inc., Nordic Laboratories Inc., Pfizer (Canada) Inc., Rhône-Poulenc Pharmaceuticals Inc., G. D. Searle of Canada, Ltd., Squibb Canada Inc., Sterling Drugs Ltd./Winthrop Laboratories, the Upjohn Company of Canada, and the University of Manitoba Pharmacology Department.

Ryanodine receptor Ca2+ release channels: does diversity in form equal diversity in function?

1996 ◽  
Vol 76 (4) ◽  
pp. 1027-1071 ◽  
Author(s):  
J. L. Sutko ◽  
J. A. Airey
Keyword(s):  
Intracellular Calcium ◽  
Ryanodine Receptor ◽  
Skeletal Muscles ◽  
Calcium Release ◽  
Cell Types ◽  
Calcium Transients ◽  
Eukaryotic Cells ◽  
Calcium Release Channels ◽  
Primary Focus ◽  
Fast Twitch

Complexities in calcium signaling in eukaryotic cells require diversity in the proteins involved in generating these signals. In this review, we consider the ryanodine receptor (RyR) family of intracellular calcium release channels. This includes species, tissue, and cellular distributions of the RyRs and mechanisms of activation, deactivation, and inactivation of RyR calcium release events. In addition, as first observed in nonmammalian vertebrate skeletal muscles, it is now clear that more than one RyR isoform is frequently coexpressed within many cell types. How multiple ryanodine receptor release channels are used to generate intracellular calcium transients is unknown. Therefore, a primary focus of this review is why more than one RyR is required for this purpose, particularly in a tissue, such as vertebrate fast-twitch skeletal muscles, where a relatively simple and straightforward change in calcium would appear to be required to elicit contraction. Finally, the roles of the RyR isoforms and the calcium release events they mediate in the development of embryonic skeletal muscle are considered.

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