Ca2+extrusion from rabbit inferior vena cava smooth muscle was studied using ratiometric fura 2 fluorimetry. Concomitant blockade of the plasma membrane Ca2+-adenosinetriphosphatase (ATPase; PCMA), Na+-Ca2+exchanger, and sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) completely prevented the decline in intracellular Ca2+ concentration ([Ca2+]i) normally observed when Ca2+ is removed from the ex...

Cardiac muscle fails to relax upon replacement of extracellular Ca2+ with Ba2+. Among the manifold consequences of this intervention, one major possibility is that Na(+)-Ba2+ exchange is inadequate to support normal relaxation. This could occur due to reduced transport rates of Na(+)-Ba2+ exchange and/or by failure of Ba2+ to activate the exchanger molecule at the high affinity regulatory Ca2+ ...

The widely accepted model to explain the positive inotropic effect of cardiac glycosides invokes altered Na+-Ca2+ exchange activity secondary to Na+ pump inhibition. However, proof of this model is lacking and alternative mechanisms have been proposed. We directly tested the role of the Na+-Ca2+ exchanger in the action of the glycoside ouabain using Na+-Ca2+ exchanger knockout mice. Ablation of...

The effects of parathyroid hormone were studied on Ca2+ fluxes in canine renal proximal tubular basolateral membrane vesicles (BLMV). Efflux of Ca2+ from preloaded BLMV was found to be stimulated by an external Na+ gradient, and this was inhibited by the Na+ ionophore, monensin, and enhanced by intravesicular negative electrical potentials, which indicated electrogenic Na+/Ca2+ exchange activit...

Kopper, Kara L., and Joseph S. Adorante. Regulation of intracellular calcium in N1E-115 neuroblastoma cells: the role of Na /Ca2 exchange. Am J Physiol Cell Physiol 282: C1000–C1008, 2002; 10.1152/ajpcell.00182.2001.—In fura 2-loaded N1E-115 cells, regulation of intracellular Ca2 concentration ([Ca2 ]i) following a Ca2 load induced by 1 M thapsigargin and 10 M carbonylcyanide p-trifluoromethyox...

The role of sodium-calcium exchanger in calcium homeostasis in Bergmann glial cells in situ was investigated by monitoring cytoplasmic calcium ([Ca2+]i) and sodium ([Na+]i) concentrations. The [Ca2+]i and [Na+]i transients were measured either separately by using fluorescent indicators fura-2 and SBFI, respectively, or simultaneously using the indicators fluo-3 and SBFI. Since the removal of ex...

The Ca2+ indicator photoprotein, aequorin, was used to estimate and monitor intracellular Ca2+ levels in Limulus ventral photoreceptors during procedures designed to affect Na+/Ca2+ exchange. Dark levels of [Ca2+]i were estimated at 0.66 +/- 0.09 microM. Removal of extracellular Na+ caused [Ca2+]i to rise transiently from an estimated 0.5-0.6 microM in a typical cell to approximately 21 microM;...