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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 78 (1983), S. 289-297 
    ISSN: 1435-1803
    Keywords: tyramine ; myocardial lesions ; myocardial ultrastructure ; creatinkinase isoenzyme ; creatinkinase activity ; Sprague-Dawley rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The authors performed an experimental study on myocardial injury induced by tyramine. For this purpose Sprague-Dawley male rats received multiple dose levels of tyramine hydrochloride. The drug exerts its sympathomimetic effects chiefly by the release of catecholamines stored in nerve endings. Myocardial lesions were documented on the basis of serum creatinkinase isoenzyme (MB-CK) changes and creatinkinase activity (CK) depletion in homogenate of cardiac tissue in animals sacrificed at different time intervals from tyramine injection. Accordingly, MB-CK values expressed as IU/l×103 (mean±standard error of the mean, [SEM]) assessed at the 2nd and 4th hours from 50, 100, or 150 mg i.p. tyramine/100 g body weight were 0.99±0.23 or 0.85±0.30 (50 mg), 1.75±0.24 or 8.50±0.41 (100 mg), 2.07±0.60 or 8.40±0.39 (150 mg), respectively. Values in control animals were 0.51±0.07. As shown, the most marked increase in MB-CK levels is obtained at the 4th hour in 100 mg/100 g b.w. tyramine-treated rats. Thus MB-CK values were also explored at the 6th (7.43±0.15) and 12th (2.24±0.23) hours from drug administration. A significant (p〈0.001) rise in serum MB-CK levels can be observed reaching the peak at the 4th hour after tyramine (100 mg/100 g b.w.). Moreover, the CK myocardial content (IU/mg of protein) in the same tyramine-animals at the 2nd or 4th hours from 50, 100 or 150 mg of the i.p. drug/100 g b.w. were (mean ± SEM) 11.10±0.05 or 9.26±0.57 (50 mg), 9.42±0.81 or 8.57±0.22 (100 mg), 8.92±2.17 or 6.70±0.04 (150 mg), respectively. At the 6th or 12th hours from i.p. tyramine (100 mg/100 g b.w.) CK values were 9.60±0.48 or 9.99±0.56. Control values showed 13.50±0.68. A significant (p〈0.001) decrease in CK myocardial content in the rats treated by the drug was achieved with the most marked CK depletion 4 hours after receiving tyramine (100 mg/100 g b.w.). On these bases, the ultrastructural changes were investigated in tyramine-treated rats (100 mg/100 g b.w.) at the 4th hours from the drug administration. The finding included mitochondrial and myofibrillar damage. In conclusion, this experimental model accounts for the possibility to induce myocardial damagein vivo in tyramine-treated rats.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 75 (1980), S. 757-763 
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An männlichen Sprague-Dawley-Ratten (200–220 g) wurden die Effekte einer Ca++-antagonistischen Substanz auf die hypoxiebedingte Hypertrophie des Myokards untersucht. Die Tiere wurden in einer Unterdruckkammer einem reduzierten Luftdruck ausgesetzt. Die Ratten wurden zwei Gruppen aufgeteilt und unter akutem oder chronisch intermittierendem Sauerstoffmangel gehalten (0,42 Atmosphären für 24 Stunden bzw. 0,42 Atmosphären für 12 Studen täglich über 10 Tage). Verapamil (VRP) wurde in einer Gesamtdosis von 200 mg/kg Körpergewicht subkutan verabfolgt. Bei hypoxischen Ratten reduzierte die Substanz die Werte für das Trockengewicht des Herzens, bezogen auf das Körpergewicht, erheblich. Dieses Phänomen ist wahrscheinlich zu beziehen auf: 1. eine verminderte Aktiverung des kontraktilen Systems mit Abnahme der ATP-Spaltung als Ergebnis einer Blockade des Ca++-Influx in der Myokardzelle; 2. den Effekt von Verapamil auf die hypoxiebedingte pulmonalenm Hypertension und/oder 3. einen direkten Effekt der Substanz auf die Myokardzelle.
    Notes: Summary Male Sprague-Dawley rat (200–220 g) were employed, to study the effect of a calcium antagonistic drug on hypoxia-induced myocardial hypertrophy. The hypoxic condition was obtained by exposure of animals to reduced barometric pressure in a hypobaric chamber. The rats, divided in groups, were exposed to acute or chronic intermittent hypoxia (0.42 atmospheres of air for 24 hrs or 0.42 atm for 12 hrs per day for 10 days, respectively). Verapamil (VRP) was given subcutaneously in a total dose of 200 mg/kg/b.w./rat. In hypoxic rats, the durg significantly reduced the values of dry heart weight calculated on the basis of its relationship to total body weight. This phenomenon is probably due to: (1) reduced activation of the contractile system and a thereby resulting decrease in ATP breakdown as a result of blocking of Ca++ inflow into myocardial cells; (2) the effect of Verapamil on hypoxia-induced pulmonary hypertension and/or (3) a direct effect of the drug on the myocardial cell.
    Type of Medium: Electronic Resource
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