Calcium Flux and Contractility in Guinea Pig Atria

Winegrad, Saul; Shanes, Abraham M.

doi:10.1085/jgp.45.3.371

Cited by 305 publications

(102 citation statements)

References 28 publications

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“…Their hearts were rapidly removed and placed in a vessel containing heparinized Krebs-Henseleit (Krebs) solution (Winegrad & Shanes, 1962) previously gassed with 95% 02, 5% CO2. The composition of the solution was: NaHCO3 27-2 mM, NaCl 1180 mM, KCl 4-8 mM, KH2PO4 10 mM, MgSO47H20 1-2 mM, CaCl2-2H20 2-5 mm and glucose 11-1 mm.…”

Section: Methodsmentioning

confidence: 99%

The effects of diphenylhydantoin and potassium on the biological activity of ouabain in the guinea‐pig heart

Baskin

Dutta

Marks

1973

British J Pharmacology

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Summary1. Diphenylhydantoin (DPH) and potassium significantly prevent ouabain intoxication without preventing the inotropic effects of ouabain in the guineapig isolated heart. 2. The antiarrhythmic effect of DPH and K on ouabain-induced toxicity appears to be related to their ability to reduce ouabain accumulation by the myocardium and thereby prevent the intracellular Na and K changes which lead to the arrhythmic state.

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Section: Methodsmentioning

confidence: 99%

The effects of diphenylhydantoin and potassium on the biological activity of ouabain in the guinea‐pig heart

Baskin

Dutta

Marks

1973

British J Pharmacology

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“…Total calcium of the solution of the ash and total calcium of the nitric acid were measured with a Beckman DU spectrophotometer with a photomultiplier and an oxygen-hydrogen flame (3). The intensity at 556 m/u was used as a measure of calcium.…”

Section: B Measurement Of Calcium and Camentioning

confidence: 99%

“…Small amounts of calcium are necessary for maximum contraction and maximum adenosine-triphosphatase activity in muscle models (1,31) Associated with contraction of intact muscle fibers there is an accelerated exchange of calcium probably involving both membrane and intracellular calcium (2,3). Hill has shown on theoretical grounds that insufficient time exists between membrane depolarization and muscle activation for a substance to diffuse from the cell surface to the cell center (4).…”

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confidence: 99%

Autoradiographic Studies of Intracellular Calcium in Frog Skeletal Muscle

Winegrad

1965

The Journal of General Physiology

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126

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Autoradiographs consisting of a 1000 A thick tissue section and a 1400 A thick emulsion film have been prepared from frog toe muscles labeled with Ca 45 . The muscles had been fixed with an oxalate-containing osmium solution at rest at room temperature, at rest at 4 0°C , during relaxation following K+ depolarization or after prolonged depolarization. From 6 to 39 per cent of K+ contracture tension was produced during fixation. The grains in the autoradiographs were always concentrated in the center 0.2 to 0.3 /A of the I band and the region of the overlapping of the thick and thin filaments. The greater the tension produced during fixation, the greater was the concentration in the A band and the smaller the concentration in the I band. Autoradiographs of two muscles fixed by freeze-substitution resembled those of muscles which produced little tension during osmium fixation. Muscles which shortened during fixation produced fewer grains. In the narrow (<2.0 /j) sarcomeres of the shortened muscles, grain density decreased with decreasing sarcomere width. A theoretical analysis of the significance of these grain distributions is proposed and discussed.A considerable body of evidence has been accumulated to suggest that calcium plays a critical role in excitation-contraction coupling in muscle. Small amounts of calcium are necessary for maximum contraction and maximum adenosine-triphosphatase activity in muscle models (1, 31) Associated with contraction of intact muscle fibers there is an accelerated exchange of calcium probably involving both membrane and intracellular calcium (2, 3). Hill has shown on theoretical grounds that insufficient time exists between membrane depolarization and muscle activation for a substance to diffuse from the cell surface to the cell center (4). Therefore, the "activator" which directly initiates the contraction must either be transmitted by a process faster than diffusion or must be stored inside the cell at a site near the contractile proteins. Huxley and Taylor have shown that the membrane excitation may be con-455

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“…However, the interpretation ofexperiments designed to measure Ca2+ fluxes by using 'Ca2+ has been equivocal. Experiments with heart tissue have shown beat-dependent 'Ca2+ uptake (9)(10)(11)(12)(13)(14) but of a magnitude far greater than found in cultures of beating neonatal cells (15). In all cases, a major problem has been that the cellular Ca2+ represents such a small fraction of the total Ca2+ in the tissue that it is almost impossible to detect.…”

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confidence: 99%

Measurement of rapidly exchangeable cellular calcium in the perfused beating rat heart.

Hunter¹,

Haworth²,

Berkoff³

1981

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

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Although Ca2+ has long been known to play a vital role in excitation-contraction coupling in the heart, investigation of the details of this role has been hampered by the experimental difficulty of measuring Ca2+ movements through the different compartments ofthe cell. A major problem has been to distinguish the relatively small amount of rapidly exchangeable cellular Ca2+ from the large amount ofvascular and interstitial Ca2+. We report here a method that overcomes this problem. Rat Excitation ofthe heart induces an increase in cellular free Ca2", which then triggers myocardial contraction (1). The immediate origin of this Ca2" has been the subject of much controversy (for review, see refs. 2-5). Much of it may come from cellular stores. However, attempts to measure myocardial cellular Ca2" have met with limited success. Ca2' influx during excitation of the myocardial cell has been demonstrated electrophysiologically (6-8), although the extent of this influx is still in dispute.With the aid of aequorin, a Ca2+-sensitive fluorescent probe, a beat-to-beat fluctuation ofcytoplasmic levels offree Ca2+ has been observed in the frog heart (1). However, the interpretation ofexperiments designed to measure Ca2+ fluxes by using 'Ca2+ has been equivocal. Experiments with heart tissue have shown beat-dependent 'Ca2+ uptake (9-14) but of a magnitude far greater than found in cultures of beating neonatal cells (15). In all cases, a major problem has been that the cellular Ca2+ represents such a small fraction of the total Ca2+ in the tissue that it is almost impossible to detect. Furthermore, cellular Ca2+ fluxes occur on a time scale similar to that of vascular and interstitial washout time, so that although kinetic analysis of 'Ca2+ washout from the whole heart shows many pools (16, 17), the pool of interest is still difficult to distinguish from the extracellular pools. We have circumvented this problem by using the well-known fact that active processes have a much higher Q1o than simple diffusion. Thus, by cooling the heart after labeling with perfusate containing 'Ca2 , the cellular '5Ca2+ becomes trapped. The high background 'Caa2+ from vascular and interstitial spaces is then removed by perfusion at 6°C, so that cellular Ca2+ can readily be detected be releasing it with a second warm perfusion. METHODSLabeling of Heart with 'Ca"+. Retired female breeder rats (Sprague-Dawley) were anesthetized by intraperitoneal injection of thiamylal (100 mg/kg). The heart was excised, and cannulas were placed in the aorta and pulmonary vein. Incisions were made in the pulmonary artery and the right atria to allow adequate flow. The basal perfusate was 118 mM NaCV25 mM NaHCOV4.7 mM KCV1.2 mM KH2POd1.2 mM MgSO411 mM glucose/2.5 mM CaCl2, pH 7.4. It was bubbled with 95% 02/5% Co2 and warmed to 37°C. The heart was perfused for 10 sec through the pulmonary vein cannula to wash out any air bubbles. Then it was perfused for the remainder ofthe perfusion period through the aorta. The height ofthe reservoir was 65 cm above the hea...

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Calcium Flux and Contractility in Guinea Pig Atria

Cited by 305 publications

References 28 publications

The effects of diphenylhydantoin and potassium on the biological activity of ouabain in the guinea‐pig heart

The effects of diphenylhydantoin and potassium on the biological activity of ouabain in the guinea‐pig heart

Autoradiographic Studies of Intracellular Calcium in Frog Skeletal Muscle

Measurement of rapidly exchangeable cellular calcium in the perfused beating rat heart.

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