AIMS Contraction of the heart is regulated by electrically evoked Ca(2+) transients (CaTs). H(+) ions, the end products of metabolism, modulate CaTs through direct interactions with Ca(2+)-handling proteins and via Na(+)-mediated coupling between acid-extruding proteins (e.g. Na(+)/H(+) exchange, NHE1) and Na(+)/Ca(2+) exchange. Restricted H(+) diffusivity in cytoplasm predisposes pH-sensitive ...

This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential up...

The extent, time course, and reversibility of mitochondrial Ca2+ uptake secondary to cellular Ca2+ influx stimulated by massive Na+ efflux were evaluated by electron probe microanalysis of rabbit portal vein smooth muscle. Strips of portal vein were Na+ loaded for 3 hours at 37 degrees C in a K+-free 1 mM ouabain solution, after which rapid Na+ efflux was induced by washing with a Na+-free K+-L...

Membrane potential-current and mechanical tension of frog atrial muscle were studied in a Ca and Mg-free solution containing 1 mmol/l EGTA (Ca-free solution). Exposure to Ca-free solution resulted in a shortening of action potential duration within 1.5 min and a subsequent lengthening which were paralleled by changes in magnitude and duration of the contraction. Similarly, the slow inward curre...

The effect of the extracellular Ca depletion on potassium contracture was investigated in single fibers isolated from frog semitendinosus muscle mainly in relation to its time and Na dependency. The shortening of plateau duration and the increase in the rate of relaxation of the potassium contracture appeared within 3--5 sec and 15 sec, respectively, after the fiber was immersed in Ca-free Na R...

BACKGROUND Stretch elicits an immediate, followed by a delayed, inotropic response in various animal models and failing human myocardium. This study aimed to characterize functional differences in the stretch response between failing and nonfailing human myocardium. METHODS AND RESULTS Experiments were performed in muscle tissue from 86 failing and 16 nonfailing human hearts. Muscles were str...

Left ventricular hypertrophy (∼40%) was induced in rats by banding of the abdominal aorta. After 16 wk, ventricular homogenates were prepared for biochemical measurements and ventricular myocytes were isolated for functional studies. In myocytes, the effects of banding on intracellular Ca handling, contraction, and excitation-contraction (E-C) coupling were determined using indo 1 fluorescence ...

There are four isoforms of the α subunit (α1-4) and three isoforms of the β subunit (β1-3) of Na,K-ATPase, with distinct tissue-specific distribution and physiological functions. α2 is thought to play a key role in cardiac and smooth muscle contraction and be an important target of cardiac glycosides. An α2selective cardiac glycoside could provide important insights into physiological and pharm...

Background—Stretch elicits an immediate, followed by a delayed, inotropic response in various animal models and failing human myocardium. This study aimed to characterize functional differences in the stretch response between failing and nonfailing human myocardium. Methods and Results—Experiments were performed in muscle tissue from 86 failing and 16 nonfailing human hearts. Muscles were stret...

Flexible anionic metal-organic frameworks (MOFs) are transformed into neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs display...