The effects of KB-R7943, an inhibitor of reverse Na super(+)/Ca super(2+) exchange, on the force of contraction of papillary muscles in the heart of the ground squirrel Spermophilus undulatus

• Published in: Biophysics (Oxford) 2017-01, Vol.62 (1), p.109-114
• Main Authors: Averin, A S, Kosarsky, L S, Tarlachkov, S V, Vekhnik, V A, Averina, I V, Alekseev, A E, Fesenko, EE, Nakipova, O V
• Format: Article
• Language: English
• Subjects: Spermophilus
• ISSN: 0006-3509; 1555-6654
• DOI: 10.1134/S000635091701002X

We investigated the effect of KB-R7943, an inhibitor of the reverse mode of Na super(+)/Ca super(2+) exchanger, on the force of isometric contractions, the contractile force-frequency relationship and post-rest potentiation (a qualitative parameter of Ca super(2+) levels in sarcoplasmic reticulum) in the right ventricle papillary muscles isolated from ground squirrel hearts during summer (June, n = 4) and autumn (October, n = 4) activities. In the presence of 1.8 mM Ca2+at 36 degree C, 1-1.5 hours-long treatment of the summer papillary muscles with KB-R7943 produced no significant effects on the contractile indices at the majority of stimulation frequencies. In the autumn papillary muscles KB-R7943 induced a 40-50% decrease in the force of contraction (negative inotropic effect) at low stimulation frequencies (0.1-0.3 Hz) without any significant effect at higher stimulation frequencies (0.4-3.0 Hz). Furthermore, in this group, KB-R7943 suppressed the post-rest potentiation of contractility by 50 plus or minus 21% at pause durations exceeding 120 s. These observations indicate that KB-R7943 can affect Ca super(2+) levels in sarcoplasmic reticulum and that Na super(+)/Ca2 super(+) exchange may contribute to the physiological remodeling of intracellular Ca super(2+) homeostasis in myocardium of hibernating animals prior their transition to a hypometabolic torpid state.