Cooper, P. J., M.-L. Ward, P. J. Hanley, G. R. Denyer, and D. S. Loiselle. Metabolic consequences of a species difference in Gibbs free energy of Na/Ca exchange: rat versus guinea pig. Am J Physiol Regulatory Integrative Comp Physiol 280: R1221–R1229, 2001.—The Gibbs free energy of the sarcolemmal Na/Ca exchanger (DGNa/Ca) determines its net Ca flux. We tested the hypothesis that a difference o...

A high cytoplasmic Na concentration may contribute to Nmethyl-D-aspartate (NMDA)-induced excitotoxicity by promoting Ca influx via reverse operation of the Na/Ca exchanger (NaCaX), but may simultaneously decrease the electrochemical Ca driving force by depolarizing the plasma membrane (PM). Digital fluorescence microscopy was used to compare the effects of Na versus ions that do not support the...

Values for ionized [Ca] in squid axons were obtained by measuring the light emission from a 0.1-mul drop of aequorin confined to a plastic dialysis tube of 140-mum diameter located axially. Ionized Ca had a mean value of 20 x 10(-9) M as judged by the subsequent introduction of CaEGTA/EGTA buffer (ratio ca. 0.1) into the axoplasm, and light measurement on a second aequorin drop. Ionized Ca in a...

This study examined the mechanism by which amiloride dissociates Na and Ca transport in distal convoluted tubules. Control rates of Na uptake averaged 288 nmol/(min mg protein) and were inhibited 39% by microM amiloride. Amiloride had no effect on Cl uptake. Resting membrane voltage, measured with the voltage-sensitive dye DiOC6 (3), averaged -70 mV. Amiloride hyperpolarized cells in a reversib...

One of the main aims of water resource planners and managers is to estimate and predict the parameters of groundwater quality so that they can make managerial decisions. In this regard, there have many models developed, proposing better management in order to maintain water quality. Most of these models require input parameters that are either hardly available or time-consuming and expensive to...

Intracellular Ca(2+) is critical to the central clock of the suprachiasmatic nucleus (SCN). However, the role of Na(+)/Ca(2+) exchanger (NCX) in intracellular Ca(2+) concentration ([Ca(2+)]i) homeostasis in the SCN is unknown. Here we show that NCX is an important mechanism for somatic Ca(2+) clearance in SCN neurons. In control conditions Na(+)-free solution lowered [Ca(2+)]i by inhibiting TTX...

Calcium (Ca) dynamics are incorporated into a mathematical model of the principal cell in the cortical collecting tubule developed earlier in Strieter et al. (1992a. Am. J Physiol. 263:F1063-1075). The Ca components are modeled after the Othmer-Tang model for IP(3)-sensitive calcium channels (1993, in Experimental and Theoretical Advances in Biological Pattern Formation, 295-319). There are IP(...