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  • 1
    ISSN: 1432-1912
    Keywords: Sympathomimetic Amines ; pH ; 45Calcium Uptake ; Contraction Force ; Guinea-Pig Atria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated, electrically stimulated left guinea-pig atria were incubated at 30° C in a Tyrode solution, the hydrogen ion concentration of which was varied by altering the percentage of the aerating CO2/O2-mixture. The increase of the extracellular hydrogen ion concentration from pH 8.0 to pH 7.0 caused a reduction of the 45calcium uptake and of the contraction force. The positive inotropic effect and the concomitantly occuring increased 45calcium uptake induced by isoprenaline and tyramine were markedly diminished at the lower pH, the response to tyramine being more affected by increased hydrogen ion concentration than that of isoprenaline. This is possibly due to a decrease in noradrenaline available at pH 7.0 for release by tyramine. Isoprenaline and tyramine enhanced the relative specific 45calcium activity (RSA) without altering the total tissue calcium content. On the contrary, the increase of the extracellular calcium concentration caused an augmentation of the relative specific 45calcium activity and the total tissue calcium content.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Research in experimental medicine 159 (1972), S. 65-74 
    ISSN: 1433-8580
    Keywords: Cardioactive glycosides ; Respiratory acidosis ; Alcalosis ; β-sympatholytic drugs ; Herzwirksame Glykoside ; Respiratorische Acidose ; Alkalose ; β-Sympathicolytica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An narkotisierten Katzen wurde der Einfluß des Blut-pH auf die Toxicität herzwirksamer Glykoside untersucht. An isolierten Vorhofpräparaten wurden in Ergänzung hierzu Versuche mit Änderung des pH der Tyrodelösung durchgeführt. 1. An Katzen wird durch eine respiratorische Acidose (pH 7,0) die Toxicität des Digitoxins, Digoxins und k-Strophanthins signifikant erhöht; dabei ist die Toxicität des Digitoxins stärker erhöht als die des Digoxins und k-Strophanthins. 2. Vorbehandlung mit Reserpin oder Practolol vermindert die Toxicität des Digitoxins in Acidose wesentlich stärker als bei normalem pH. 3. Eine durch Tris-Infusion erzeugte Alkalose von pH 7,6 bewirkt keine Änderung, eine durch Infusion von NaHCO3 erzeugte Alkalose von pH 7,6 verursacht eine geringfügige Steigerung der Digitoxintoxicität. 4. Am isolierten Vorhofpräparat des Meerschweinchens ist die Toxicität des Digitoxins, Digoxins und k-Strophanthins bei pH-Werten der Tyrodelösung von 7,0 und 7,8 nicht signifikant verschieden.
    Notes: Summary In anaesthetized cats the influence of blood-pH on the toxicity of cardiac glycosides was studied. In isolated guinea pigs atrias further experiments were performed by changing the pH of the tyrode solution. 1. In cats with respiratory acidosis (pH 7.0) the toxicity of digitoxin, digoxin and k-strophanthin is enhanced — thereby the toxicity of digitoxin is more enhanced than that of digoxin and k-strophanthin. 2. Pretreatment with reserpine or practolol diminishes the toxicity of digitoxin in acidosis more than at normal blood-pH. 3. An alcalosis of pH 7.6, produced by the infusion of tris causes no change, an alcalosis of pH 7.6 produced by the infusion of NaHCO3 causes a small increase of the toxicity of digitoxin. 4. In the isolated guinea pigs atria the toxicity of digitoxin, digoxin and kstrophanthin is not different at pH 7.0 and 7.8 of the tyrode solution.
    Type of Medium: Electronic Resource
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