Die Calcium-Umsatzgeschwindigkeit ruhender und kontrahierender Vorhofmuskulatur in vitro

Hoditz, H.; Luellmann, H

doi:10.1007/bf00412611

Cited by 44 publications

(4 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although there is much evidence from tracer experiments that Ca influx in cardiac muscle is greatly increased during excitation (Winegrad & Shanes, 1962;Langer & Brady, 1963;Niedergerke, 1963b;Hoditz & Lullmann, 1964) very little is known about the mechanisms by which the intracellular Ca-concentration is kept constant. Ca moves down a large electrochemical gradient into the heart cell, thus contributing to the total depolarizing membrane current during excitation (Niedergerke & Orkand, 1966;Reuter, 1966Reuter, , 1967.…”

Section: Introductionmentioning

confidence: 99%

The dependence of calcium efflux from cardiac muscle on temperature and external ion composition

Réuter¹,

Seitz²

1968

The Journal of Physiology

942

426

View full text Add to dashboard Cite

SUMMARY1. Exchangeable Ca in guinea-pig auricles and ventricular trabeculae of sheep and calf hearts was labelled with 45Ca and the loss of radioactivity into inactive rinsing solutions of different ion composition was measured for periods up to 6 hr. At no time did the decrease of radioactivity in the muscle follow a single exponential course, while the rate coefficient k (= fraction of 45Ca lost per minute from muscle into rinsing solution) decreased slightly with time.2. On the basis of the temperature-sensitivity of Ca efflux from auricles the activation energy has been calculated to have a value of 5900 cal/mole, corresponding to a Qlo of 135. 2,4-Dinitrophenol (5.5 x 10-5-55 x 104 M) had either no effect on Ca efflux or increased it slightly.3. Compared to control efflux in 1-8 mm [Ca]. Ca efflux decreased to 70 % in Ca-free solution, to 20 % in Ca-free, Na-free solution and to 65 % in Ca-containing, Na-free solution, NaCl being replaced by either sucrose or LiCl. Quantitatively, Ca efflux from auricles has been shown to depend to a large extent on the ratio [Ca2+]0/[Na+]'. The affinity for Na of the activation site for Ca efflux (carrier) is much less than for Ca.4. The efflux from muscles soaked for about 2 hr in Ca-free solution was not linearly related to Ca-concentration in the tissue but followed a square law.5. While Ca content in auricles increased in Ca-containing, Na-poor solution it decreased again when Tyrode solution was readmitted indicating a Na-sensitive Ca net transport in cardiac muscle.6. The results are interpreted in terms of a modified exchange diffusion mechanism (Ussing, 1947) which is responsible for Ca extrusion from mammalian cardiac muscle.

show abstract

Section: Introductionmentioning

confidence: 99%

The dependence of calcium efflux from cardiac muscle on temperature and external ion composition

Réuter¹,

Seitz²

1968

The Journal of Physiology

942

426

View full text Add to dashboard Cite

show abstract

“…While the distribution of calcium in the cardiac muscle has been analyzed either in the atrial or ventricular muscle (WINEGRAD and SHANES, 1962;GROSSMAN and FURCHGOTT, 1964;HODITZ and LULLMANN, 1964;LANGER, 1964;SHINE et al, 1971), a comparison of the distribution of calcium between the atrial and ventricular muscle has not been carried out so far. In the previous work (FUKUDA, 1972), it was found that the toad atrium contained more calcium than the ventricle and that these two tissues responded differently to excess calcium in Ringer solution.…”

mentioning

confidence: 99%

Difference in Calcium Content of Atrial and Ventricular Muscle

Fukuda

1975

Jpn.J.Physiol

View full text Add to dashboard Cite

The calcium content and inulin space of the atrial and ventricular muscle were determined in isolated perfused heart of the toad, bullfrog, guinea pig, rat, and cat. In all species studied, the total and "cellular" calcium content of the atrium were higher than those of the ventricle. A high calcium content of the atrial muscle was also observed in fresh unperfused hearts. The total calcium content of atrial and ventricular muscles increased when extracellular phosphate concentration was increased. When severe ventricular arrhythmia such as fibrillation occurred during perfusion, the total calcium content of the ventricle increased. The decay of tissue calcium content with calcium washout was examined in the toad, guinea pig, and rat heart. It was revealed that about 80 percent of total calcium existed as "exchangeable" calcium in both atrial and ventricular muscles. When the extracellular calcium concentration ([Ca]0) was altered in the toad, guinea pig, and rat heart preparation, the cellular calcium content of atrial muscle varied in proportion to [Ca])0 whereas that of ventricular muscle remained fairly constant at a higher [Ca]0 value. The development of contractile tension in the atrial and ventricular muscles at various [Ca]0 values corresponded well to these changes in the cellular calcium content except for the rat ventricle in which the contractile tension was almost proportional to [Ca]0. The relationship between the development of contractile tension and the level of cellular calcium content or [Ca]0 was discussed.

show abstract

“…Left atria were prepared according to Hoditz & Liillmann (1964). Guinea pigs of either sex weighing between 250-400 g were sacrificed by a blow on the neck, exsanguinated and the hearts rapidly excised.…”

Section: Methodsmentioning

confidence: 99%

A Method for Simultaneous Evaluation of Drug‐Effects on Excitability and Inotropy in Isolated Cardiac Preparations

Lange-Asschenfeldt

Mescheder

Mohr

1992

Pharmacology & Toxicology

View full text Add to dashboard Cite

A method is described which allows determination of the threshold of excitability of electrically stimulated, regularly contracting isolated cardiac preparations. The force of the contraction (CF) is isometrically recorded and serves as feed-back signal indicating effective stimulation. The pulse intensity is decreased monoexponentially as long as contractions are elicited. If the mechanical response does not occur, the pulse intensity is immediately reset to the initial high value and the pulse is delivered with a latency of a few milliseconds. A stimulus intensity just below threshold is recorded as the rectangular pulse threshold (RPT). The method was applied in order to compare the effects of a number of antiarrhythmic drugs including the beta-blocker propranolol on the electrical excitability (1/RPT) and on the contractility of guinea pig left atria stimulated at 3 Hz. In general, the drugs depressed excitability and contractility concomitantly. The rank order of potency with respect to the reduction of excitability was: aprindine greater than propafenone greater than propranolol greater than quinidine greater than mexilitine greater than lidocaine. The Ca-antagonist verapamil reduced contractile force most powerful but had no effect on excitability. Presumably, RPT reflects sodium-channel function. In conclusion, the described method offers an easily operable test of drug effects on the excitability threshold and the contractility of isolated cardiac preparations.

show abstract

Die Calcium-Umsatzgeschwindigkeit ruhender und kontrahierender Vorhofmuskulatur in vitro

Cited by 44 publications

References 13 publications

The dependence of calcium efflux from cardiac muscle on temperature and external ion composition

The dependence of calcium efflux from cardiac muscle on temperature and external ion composition

Difference in Calcium Content of Atrial and Ventricular Muscle

A Method for Simultaneous Evaluation of Drug‐Effects on Excitability and Inotropy in Isolated Cardiac Preparations

Contact Info

Product

Resources

About