Bullfrog sympathetic ganglion cells were capable of producing action potentials (Ca spikes) in an isotonic (84 mM) CaCl2 solution. The peak level of Ca spikes showed an approximately 30 mv increase with a 10-fold increase in the Ca concentration. Na as well as Ca ions were capable of acting as charge carriers during the production of action potentials in a solution containing relatively high Ca...

BACKGROUND The Na(+)/Ca(2+) exchange (NCX) extrudes Ca(2+) from cardiac myocytes, but it can also mediate Ca(2+) influx, load the sarcoplasmic reticulum with Ca(2+), and trigger Ca(2+) release from the sarcoplasmic reticulum. In ischemia/reperfusion or digitalis toxicity, increased levels of intracellular [Na(+)] ([Na(+)](i)) may raise levels of intracellular [Ca(2+)] ([Ca(2+)](i)) via NCX, lea...

Ouabain, a specific inhibitor of the Na /K -pump, has previously been shown to interfere with intercellular communication. Here we test the hypothesis that the communication between vascular smooth muscle cells is regulated through an interaction between the Na /K -pump and the Na /Ca -exchanger leading to an increase in the intracellular calcium concentration ([Ca ]i) in discrete areas near th...

Ouabain, a specific inhibitor of the Na(+)/K(+)-pump, has previously been shown to interfere with intercellular communication. Here we test the hypothesis that the communication between vascular smooth muscle cells is regulated through an interaction between the Na(+)/K(+)-pump and the Na(+)/Ca(2+)-exchanger leading to an increase in the intracellular calcium concentration ([Ca(2+)](i)) in disc...

Phospholemman (PLM), a member of the FXYD family of regulators of ion transport, is a major sarcolemmal substrate for protein kinases A and C in cardiac and skeletal muscle. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. Functionally, when phosphorylated at serine(68), PLM stimulates Na(+)-K(+)-ATPase but inhib...

NG2 cells originate from various brain regions and migrate to their destinations during early development. These cells express voltage-gated Na(+) channels but fail to produce typical action potentials. The physiological role of Na(+) channels in these cells is unclear. We found that GABA induces membrane depolarization and Ca(2+) elevation in NG2 cells, a process requiring activation of GABA(A...

Hirota S, Pertens E, Janssen LJ. The reverse mode of the Na /Ca exchanger provides a source of Ca for store refilling following agonist-induced Ca mobilization. Am J Physiol Lung Cell Mol Physiol 292: L438–L447, 2007. First published October 13; doi:10.1152/ajplung.00222.2006.—Agonist-induced contraction of airway smooth muscle (ASM) can be triggered by an elevation in the intracellular Ca conc...

Sedova, Marina, Elena N. Dedkova, and Lothar A. Blatter. Integration of rapid cytosolic Ca signals by mitochondria in cat ventricular myocytes. Am J Physiol Cell Physiol 291: C840–C850, 2006. First published May 24, 2006; doi:10.1152/ajpcell.00619.2005.—Decoding of fast cytosolic Ca concentration ([Ca ]i) transients by mitochondria was studied in permeabilized cat ventricular myocytes. Mitochon...

Na(+)/Ca(2+) exchangers are low-affinity, high-capacity transporters that rapidly transport calcium against a gradient of Na(+) ions. Na(+)/Ca(2+) exchangers are divided into three groups based upon substrate specificity: Na(+)/Ca(2+) exchangers (NCX), Na(+)/Ca(2+)/K(+) exchangers (NCKX), and Ca(2+)/cation exchangers (NCLX). In mammals, there are three NCX genes, five NCKX genes, and a single N...

Decoding of fast cytosolic Ca(2+) concentration ([Ca(2+)](i)) transients by mitochondria was studied in permeabilized cat ventricular myocytes. Mitochondrial [Ca(2+)] ([Ca(2+)](m)) was measured with fluo-3 trapped inside mitochondria after removal of cytosolic indicator by plasma membrane permeabilization with digitonin. Elevation of extramitochondrial [Ca(2+)] ([Ca(2+)](em)) to >0.5 microM res...