Na-Ca exchange is proposed to be an important regulator of myoplasmic intracellular Ca concentration ([Ca]|) and contraction in vascular smooth muscle. We investigated the role of Na-Ca exchange in regulating [Ca], in swine carotid arterial tissues that were loaded with aequorin to allow simultaneous measurement of [Ca], and force. Reversal of Na-Ca exchange, by reduction of extracellular Na co...

Na(+)-Ca2+ exchange is proposed to be an important regulator of myoplasmic intracellular Ca2+ concentration ([Ca2+]i) and contraction in vascular smooth muscle. We investigated the role of Na(+)-Ca2+ exchange in regulating [Ca2+]i in swine carotid arterial tissues that were loaded with aequorin to allow simultaneous measurement of [Ca2+]i and force. Reversal of Na(+)-Ca2+ exchange, by reduction...

AIMS Brain-type alpha-subunit isoforms of the Na(+) channel are present in various cardiac tissue types and may control pacemaker activity and excitation-contraction coupling. Heart failure (HF) alters pacemaker activity and excitation-contraction coupling. Here, we studied whether HF alters brain-type Na(+) channel properties. METHODS AND RESULTS HF was induced in rabbits by volume/pressure ...

Na-Ca exchange is proposed to be an important regulator of myoplasmic intracellular Ca concentration ([Ca]|) and contraction in vascular smooth muscle. We investigated the role of Na-Ca exchange in regulating [Ca], in swine carotid arterial tissues that were loaded with aequorin to allow simultaneous measurement of [Ca], and force. Reversal of Na-Ca exchange, by reduction of extracellular Na co...

Excitation-contraction (E-C) coupling was investigated in rat hearts 6 wk after induction of myocardial infarction (MI) by ligation of the left coronary artery. Heart weight was increased by 74% and left ventricular end-diastolic pressure was 23 +/- 2 mmHg in MI compared with 8 +/- 2 mmHg in sham-operated controls (Sham, P < 0.001). Cell shortening was measured in voltage-clamped myocytes at 36...

Hypertrophy and failure (H/F) in humans and large mammals are characterized by a change from a positive developed force-frequency relationship (+FFR) in normal myocardium to a flattened or negative developed force-frequency relationship (-FFR) in disease. Altered Ca(2+) homeostasis underlies this process, but the role of intracellular Na(+) concentration ([Na(+)](i)) in H/F and frequency-depend...

The Brugada syndrome (BrS) is a right ventricular (RV) arrhythmia that is responsible for up to 12% of sudden cardiac deaths. The aims of our study were to determine the cellular mechanisms of the electrical abnormality in BrS and the potential basis of the RV contractile abnormality observed in the syndrome. Tetrodotoxin was used to reduce cardiac Na(+) current (I(Na)) to mimic a BrS-like sett...

The physiological significance of the cardiac glycoside-binding site on the Na,K-ATPase remains incompletely understood. This study used a gene-targeted mouse (alpha2(R/R)) which expresses a ouabain-insensitive alpha2 isoform of the Na,K-ATPase to investigate whether the cardiac glycoside-binding site plays any physiological role in active Na(+)/K(+) transport in skeletal muscles or in exercise...

Systematic crystal structure refinements from powder X-ray diffraction data as well as density functional theory calculations demonstrate that the silicon clathrate II Si(cF136) exhibits a lattice contraction as Na is introduced solely into the Si(28) cages. When the Si(20) cages, in addition, begin to be filled with Na, a contrasting lattice expansion results. The nonmonotonic structural respo...