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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 275 (1972), S. 359-371 
    ISSN: 1432-1912
    Keywords: k-Strophanthin ; Digitoxigenin ; 45Calcium ; Contractile Force ; Cellular Calcium Content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of positive inotropic and of toxic concentrations of k-strophanthin and digitoxigenin on contractile force, calcium content and 45calcium exchange was studied in isolated guinea-pig atria; at the same time the extracellular space of each preparation was determined. 1. In the concentration range used (0.8–13.4 μM) the two agents did not show any effect on the extracellular space. 2. Positive inotropic concentrations of k-strophanthin and digitoxigenin induced a significant decrease in the cellular calcium content as a result of a net increase in calcium efflux. At 3, 5, 10 or 15 min after the addition of the drug the relative specific 45calcium activity (RSA) was increased and was significantly greater than values obtained in control experiments. It is concluded that positive inotropic concentrations enlarge the exchangeable calcium fraction of the myocardial cell. 3a. During the initial positive inotropic phase of action of toxic concentrations of k-strophanthin (2.67 and 13.4 μM) and digitoxigenin (2.67 μM) there was also a significant decrease of the cellular calcium content, which occured more rapidly than that produced by positive inotropic concentrations. 3b. After the occurrence of toxic signs the calcium content of the myocardial cell was significantly increased while the unexchanged calcium fraction remained unchanged in absolute size. The RSA was always significantly increased compared with results from control experiments. It is concluded that the action of toxic concentrations of k-strophanthin and digitoxigenin on the calcium metabolism is due to a marked reduction in calcium efflux. 4. Digitoxigenin increased the contractile force considerably more than k-strophanthin, but had less effect on calcium metabolism. The difference might be due to the different lipophilic properties of the two agents.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Clinical and experimental medicine 154 (1971), S. 165-176 
    ISSN: 1591-9528
    Keywords: Blood-pH ; resp. Acidosis ; Cardiovascular Drugs ; Blut-pH ; resp. Acidose ; kreislaufaktive Pharmaka
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Elektrisch gereizte Vorhofpräparate des Meerschweinchens wurden in einem Tyrodebad suspendiert, dessen pH durch Begasung mit verschiedenen CO2-Konzentrationen auf 7,0, 7,4 bzw. 7,8 eingestellt wurde. Kontraktionskraft und maximale Kontraktionsgeschwindigkeit der Vorhöfe wurden durch diese pH-Änderungen nicht beeinflußt. Der positiv inotrope Effekt von Tyramin, Isoproterenol und Calcium war bei pH 7,0 abgeschwächt, bei pH 7,8 verstärkt. An narkotisierten Katzen wurde durch Beatmung mit 10 bzw. 20% CO2 eine respiratorische Acidose mit pH-Werten von 7,15 bzw. 7,0 erzeugt. Dabei traten eine mäßige Zunahme der Herzfrequenz, der maximalen Druckanstiegsgeschwindigkeit (dp/dtmax) und des systolischen Femoralisdruckes ein. Die Wirkung aller untersuchten Pharmaka war in Acidose abgeschwächt, wobei sich aber folgende quantitative und qualitative Unterschiede ergaben: 1. Die blutdrucksenkende Wirkung des Isoproterenols und die blutdrucksteigernde Wirkung des Noradrenalins waren stärker abgeschwächt als ihre positiv inotrope Wirkung am Herzen. 2. Die pressorische Wirkung des Angiotensins und Noradrenalins war weniger beeinträchtigt als die des Naphazolins. 3. Die blutdrucksenkende Wirkung des Acetylcholins war im Gegensatz zu der des Isoproterenols weniger abgeschwächt.
    Notes: Summary Experiments were performed on guinea pigs isolated atria which were stimulated electrically. If the pH of the tyrode solution was changed by variation of pCO2 no alteration of force of contraction and maximal velocity of contraction (dT/dtmax.) occured. The inotropic effects of tyramine, isoproterenol and calcium were diminished at pH 7.0 and increased at pH 7.8. During respiratory acidosis (pH 7.0) anaesthetized cats showed a small increase in heart rate, left ventricular dp/dtmax. and arterial blood pressure. The effects of all tested drugs were diminished in acidosis, whereby the following qualitative and quantitative differences appeared: 1. The depressive effect of isoproterenol and the stimulating effect of norepinephrine on arterial blood pressure were much more diminished than the positive inotropic effect of these drugs. 2. The effect of angiotensin and norepinephrine on arterial blood pressure was less affected than that of naphazoline. 3. The effect of acetylcholine on arterial blood pressure was scarcely diminished in contrast to that of isoproterenol.
    Type of Medium: Electronic Resource
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