TRPC3 has been suggested as a key component of phospholipase C-dependent Ca signaling. Here we investigated the role of TRPC3-mediated Na entry as a determinant of plasmalemmal Na /Ca exchange. Ca signals generated by TRPC3 overexpression in HEK293 cells were found to be dependent on extracellular Na , in that carbachol-stimulated Ca entry into TRPC3 expressing cells was significantly suppresse...

Reduction of the transsarcolemmal [Na] gradient in rabbit cardiac muscle leads to an increase in the force of contraction. This has frequently been attributed to alteration of Ca movements via the sarcolemmal Na/Ca exchange system. However, the specific mechanisms that mediate the increased force at individual contractions have not been clearly established. In the present study, the [Na] gradie...

Phosphorylation of Na channels has been suggested to increase their Ca permeability. Termed "slip-mode conductance" (SMC), this hypothesis predicts that Ca influx via protein kinase A (PKA)-modified Na channels can induce sarcoplasmic reticulum (SR) Ca release. We tested this hypothesis by determining if SR Ca release is graded with I(Na) in the presence of activated PKA (with Isoproterenol, IS...

The Senegalese sole is a marine flatfish, which often penetrates into estuarine waters to feed. It cannot, however, survive in full freshwater. The current study investigated the effect of adaptation to low salinity (10 per thousand) on olfactory responses to changes in environmental [Ca(2+)] and [Na(+)] and amino acids by the electro-encephalogram (EEG) recorded from the olfactory bulb. The so...

In order to resolve uncertainties as to the mechanisms of toxic action of Cu and the protective effects of water [Ca], juvenile rainbow trout were acclimated to baseline soft water (SW, [Na(+)]=0.07, [Ca(2+)]=0.15, [Mg(2+)]=0.05mmolL(-1)) and then exposed to Cu with or without elevated [Ca] but at constant titratable alkalinity (0.27mmolL(-1)). The 96-h LC50 was 7-fold higher (63.8 versus 9.2μg...

Mast cells rely on Ca(2+) signaling to initiate activation programs leading to release of proinflammatory mediators. The interplay between Ca(2+) release from internal stores and Ca(2+) entry through store-operated Ca(2+) channels has been extensively studied. Using rat basophilic leukemia (RBL) mast cells and murine bone marrow-derived mast cells, we examine the role of Na(+)/Ca(2+) exchangers...

Before synaptogenesis, early excitability implicating voltage-dependent and transmitter-activated channels is known to be crucial for neuronal development. We previously showed that preplate (PP) neurons of the mouse neocortex express functional Na(+) channels as early as embryonic day 12. In this study, we investigated the role of these Na(+) channels in signaling during early development. In ...

Chromaffin cells isolated from bovine adrenals and maintained in culture were loaded with 45Ca, and the mechanism of 45Ca efflux from these cells was investigated. During exposure to a Ca-deficient, Mg (1 mM)-containing medium, replacement of NaCl with sucrose, choline Cl, or Tris Cl reduced the rate of 45Ca efflux by approx. 30-40%, showing the presence of a Na-dependent 45Ca efflux mechanism....

Axons freshly dissected from living specimens of the tropical squid Dorytheutis plei have a calcium content of 68 mumol/kg of axoplasm. Fibers stimulated at 100 impulses/s in 100 mM Ca seawater increase their Ca content by 150 mumol/kg.min; axons placed in 3 Ca (choline) seawater increase their Ca content by 12 mumol/kg.min. Axons loaded with 0.2--1.5 mmol Ca/kg of axoplasm extruded Ca with a h...