We examined Ba2+ influx using isotopic and fura-2 techniques in transfected Chinese hamster ovary cells expressing the bovine cardiac Na+/Ca2+ exchanger (CK1.4 cells). Ba2+ competitively inhibited exchange-mediated 45Ca2+ uptake with a Ki approximately 3 mM. Ba2+ uptake was stimulated by pretreating the cells with ouabain and by removing extracellular Na+, as expected for Na+/Ba2+ exchange acti...

The importance of Na+/Ca2+ exchangers in the regulation of the physiological and pathological functions of the nervous system has been widely recognized. In this study, we used primary cultured E14.5 cortical neurons as a model system to study the possible roles of the reverse mode Na+/Ca2+ exchange activity in neurotransmission. Using RT-PCR, several exchanger isoforms, ncx1, ncx3 and nckx2-4 ...

Alterations in cellular Ca2+ and Na+ regulation play a role in the pathogenesis of essential hypertension. Using peripheral lymphocytes from 68 normal persons, we observed the following relationships for major cellular Ca2+ regulatory parameters. Among men and women, Na+-Ca2+ exchanger activity was positively correlated with the resting cytosolic free Ca2+ ([Ca2+]c) (r=0.43, P=0.0003), and the ...

The sarcolemmal Na(+)-Ca2+ exchanger is regulated by intracellular Ca2+ at a high affinity Ca2+ binding site separate from the Ca2+ transport site. Previous data have suggested that the Ca2+ regulatory site is located on the large intracellular loop of the Na(+)-Ca2+ exchange protein, and we have identified a high-affinity 45Ca2+ binding domain on this loop (Levitsky, D. O., D. A. Nicoll, and K...

In TTX-sensitive nerve and skeletal muscle Na+ channels, selective modification of external carboxyl groups with trimethyloxonium (TMO) or water-soluble carbodiimide (WSC) prevents voltage-dependent Ca2+ block, reduces unitary conductance, and decreases guanidinium toxin affinity. In the case of TMO, it has been suggested that all three effects result from modification of a single carboxyl grou...

BACKGROUND In the failing human heart, sarcoplasmic reticulum (SR) calcium handling is impaired, and therefore, calcium elimination and diastolic function may depend on the expression of sarcolemmal Na+-Ca2+ exchanger. METHODS AND RESULTS Force-frequency relations were studied in ventricular muscle strip preparations from failing human hearts (n=29). Protein levels of Na+-Ca2+ exchanger and S...

there is strong evidence demonstrating that nifedipine dissolved in ethanol selectively inhibits only l-type ca2+ current. in addition, acute ethanol exposure reduces voltage-dependent calcium currents. in the present study, we investigated the antagonistic effect of fixed concentration of nifedipine dissolved in different concentration of ethanol on l-type ca2+ current. in a na+-k+ free soluti...

The present studies probe the role of Ca2+ and Na+ in the stimulation-permeability coupling sequences by which antidiuretic hormone (ADH) induces a cyclic AMP (cAMP)-mediated increase in urea permeability in toad urinary bladder. The following results were obtained: (a) Removal of mucosal Na+ or Ca2+ or deletion of serosal Ca2+ did not modify ADH action. (b) Reduction of the serosal Na+ concent...