The effects of amrinone, a new cardiotonic bipyridine derivative, were compared to those isoproterenol and ouabain on maintained K+-induced contracture of isolated cat ventricualr muscle. Peak K+induced contracture force was decreased by amrinone (5.3 × 10-4 M) and isoproterenol (10-6 M), 31 ± 10% (n = 4, P ≤ 0.05) and 81 ± 5% (n = 4, P ≤ 0.05), respectively, and increased by ouabain (5.0 x 10-7 M), 60 ± 6% (n = 4, P ≤ 0.05). The effects of amrinone and ouabain on K+ contracture persisted during β-adrenergic blockade produced by nadolol (10- M) whereas isoproterenol's actions were attenuated. The effect of amrinone on K+-contracture force was concentration-related as was its modification of phasic isometric contractions (0.5 Hz). Resting tension, time to peak force and durection of isometric contraction were unchanged by amirone (5.3 × 10-6-1.6 × 10-3 M). Apparently, amrinone concomitantly Ca2+ release and sequestration or extrusion and thus the drug may not provoke cardiac toxicity by Ca2+ overload.
- Ca release
- Isolated cat ventricular muscle
- Isometric force Sequestration or extrusion
- β-Receptor blockade
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience