In fura 2-loaded N1E-115 cells, regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) following a Ca(2+) load induced by 1 microM thapsigargin and 10 microM carbonylcyanide p-trifluoromethyoxyphenylhydrazone (FCCP) was Na(+) dependent and inhibited by 5 mM Ni(2+). In cells with normal intracellular Na(+) concentration ([Na(+)](i)), removal of bath Na(+), which should result in reversal...

The endocardial endothelium is an important modulator of myocardial function. The present study demonstrates the existence of a stretch-activated Ca(2+)-permeable cation channel and of a Ca(2+)-activated K+ channel in the endocardial endothelium of the porcine right atrium. The stretch-activated channel is permeable for K+, Na+, Ca2+, and Ba2+, with mean conductances of approximately 32 pS for ...

Small changes of Na/K pump activity regulate internal Ca release in cardiac myocytes via Na/Ca exchange. We now show conversely that transient elevations of cytoplasmic Ca strongly regulate cardiac Na/K pumps. When cytoplasmic Na is submaximal, Na/K pump currents decay rapidly during extracellular K application and multiple results suggest that an inactivation mechanism is involved. Brief activ...

The effect of varying Nao and Nai on Ca efflux while maintaining the ratio Nao/Nai constant was explored in squid giant axons dialyzed with and without ATP. In the absence of ATP, the Ca efflux increased 3.4 +/- 0.2-fold when the Nao/Nai concentrations were reduced from 440/80 to 110/20 mM. In the presence of ATP a similar change did not have an appreciable effect. The inhibition of Ca efflux p...

There are considerable data to support the general hypothesis that accumulation of [Na]i during ischemia and early reperfusion leads, via Na/Ca exchange, to elevated [Ca]i, resulting in myocardial damage.1–10 Despite the strong support for the general aspects of this hypothesis, there is controversy regarding some details that have important implications for the design of therapeutic interventi...

MicroRNAs (miRNAs) play important roles in biological development and disease. Much less is known about their role in normal adult physiology. The proximal convoluted tubule (PCT) and the medullary thick ascending limb (mTAL) in the kidney consist of epithelial cells with different transport activities. We identified 55 possible miRNA-target pairs of which the miRNAs and their predicted target ...

A model is developed which requires the binding of 4 Na+ to a carrier before a Ca binding site is induced on the opposite side of the membrane. Upon binding Ca, this carrier translocates Na and Ca. The existence of partially Na-loaded but nonmobile forms for the carrier (NaX, Na2X, Na3X) suffices to explain both the activating and the inhibitory effects of Na on the Ca transport reaction. Analy...

Fish otoliths provide a record of age, growth, and environmental influences. In both trout and turbot, spatial chemical investigation of the endolymph surrounding the otolith (sagitta) showed a lack of uniformity. Proteins, [Formula: see text], and Mg2+ were significantly more concentrated in the proximal (facing the macula) than distal zone, whereas the opposite was observed for K+ and total C...

Ouabain and other cardiotonic steroids (CTS) inhibit Na(+) pumps and are widely believed to exert their cardiovascular effects by raising the cytosolic Na(+) concentration ([Na(+)](cyt)) and Ca(2+). This view has not been rigorously reexamined despite evidence that low-dose CTS may act without elevating [Na(+)](cyt); also, it does not explain the presence of multiple, functionally distinct isof...