Isotonic contraction and contracture of the isolated right rat ventricle. Effect of La3+, prenylamine, ATP, Mg2+
Slavícek, J.
Sbornik Lekarsky 77(1): 10-18
1975
ISSN/ISBN: 0036-5327 PMID: 1111055 Document Number: 85406
1. The isolated right rat ventricle was immersed in Tyrode solution (25) ml) and stimulated electrically at a frequency of 60/min. Changes in the amplitude of isotonic contractions and contractures were assessed. 2. Isotonic contractions were reduced (after Prenylamine, ATP, Mg), or suppressed (by LaCl3 = 10 mM). Contracture was caused by Prenylamine (4 mg/25 ml Tyrode solution or more). 3. Addition of 100 mM KCl (NaCl reduced equimolarily to 37 mM did not influence contracture in the presence of the investigated substances with the exception of MgCl2 = 10 to 15mM, where only the rate of development of potassium contracture was reduced. 4. After previous immersion of the tissue in the presence of LaCl3 - 10 mM and Prenylamine 1-4 mg/25 ml Tyrode solution the contracture developed after removal of NaCl (substitution by sucrose 270 mM), which, however, declined after addition of NaCl only when previously treated with Prenylamine and not when treated with La. 5. Addition of 100 mM KCl (naCl reduced to 37 mM) after previous immersion of the tissue in the presence of the investigated substances caused contracture the rate of rise of which was smaller after La than in controls: after the remaining substances it did not differ. 6. Reduction of the contracture after reduction of KCl from 100 to 5.6 mM developed only after previous immersion of the tissue in the presence of ATP and Mg and not after previous immersion in the presence of Prenylamine and La. 7. The results are compared with biochemical findings. They suggest a shift of contractile Ca in the heart.