Loading isolated rat hepatocytes with high concentrations of the fluorescent Ca2+-chelator quin-2 in the absence of extracellular Ca2+ decreases by about 3-fold the cytosolic Ca2+ concentration ([Ca2+]i). In these low [Ca2+]i cells, the initial 45Ca2+ uptake rate, assumed to represent the Ca2+ influx, is stimulated to a level close to that promoted by maximal doses of vasopressin and angiotensi...

Na+/Ca2+exchange has been investigated in squid ( Loligo pealei) rhabdomeric membranes. Ca2+-containing vesicles have been prepared from purified rhabdomeric membranes by extrusion through polycarbonate filters of 1-μm pore size. After removal of external Ca2+, up to 90% of the entrapped Ca2+ could be specifically released by the addition of Na+; this finding indicates that most of the vesicles...

The mechanism by which agonist-evoked cytosolic Ca2+ signals are terminated has been investigated. We measured the Ca2+ concentration inside the endoplasmic reticulum store of pancreatic acinar cells and monitored the cytoplasmic Ca2+ concentration by whole-cell patch-clamp recording of the Ca2+-sensitive currents. When the cytosolic Ca2+ concentration was clamped at the resting level by a high...

Although inhibition of the Na+/Ca2+ exchanger normally increases [Ca2+]i in neonatal cardiac myocytes, application of the inhibitor Ni2+ appears to reduce [Ca2+] measured by fluo-3. To investigate how the apparent reduction in [Ca2+]i occurs we examined Ca2+ transport by the human Na+/Ca2+ exchanger expressed in Sf9 cells. Transport of Ca2+ by the Na+/Ca2+ exchanger was examined using a laser-s...

Sarcoplasmic reticulum vesicles were preloaded with either 45Ca2+ or unlabeled Ca2+. The unidirectional Ca2+ efflux and influx, together with Ca2+-dependent ATP hydrolysis and phosphorylation of the membrane-bound (Ca2+, Mg2+)-ATPase, were determined in the presence of ATP and ADP. The Ca2+ efflux depended on ATP (or ADP or both). It also required the external Ca2+. The Ca2+ concentration depen...

The relationship between the concentration of cytosolic free Ca2+ ([Ca2+]i) and secretion of parathyroid hormone (PTH) was investigated in isolated bovine parathyroid cells using the fluorescent Ca2+ indicator, quin 2. Increasing the concentration of extracellular Ca2+ from 0.5 to 2.0 mM caused a 3-fold increase in [Ca2+]i (from 183 +/- 4 to 568 +/- 21 nM) which was associated with a 2-4-fold d...

CA2 (Continuum Analysis, 2- dimensional) is a computer program developed by the author. CA2 can solve a variety of complex geotechnical problems using explicit finite difference method. In this paper, an introduction will be given to the theoretical and numerical basis of the program and the capability of the code will be shown by solving a few interesting nonlinear and transient problems. Fina...

L-type Ca2+ channels select for Ca2+ over sodium Na+ by an affinity-based mechanism. The prevailing model of Ca2+ channel permeation describes a multi-ion pore that requires pore occupancy by at least two Ca2+ ions to generate a Ca2+ current. At [Ca2+] < 1 microM, Ca2+ channels conduct Na+. Due to the high affinity of the intrapore binding sites for Ca2+ relative to Na+, addition of microM conc...

OBJECTIVE Mitochondrial [Ca2+] ([Ca2+]m) rises in parallel with cytosolic [Ca2+] ([Ca2+]c) following ATP-depletion rigor contracture induced by hypoxia in isolated cardiomyocytes. We investigated the pathways involved in the hypoxia induced changes in [Ca2+]m by using known inhibitors of mitochondrial Ca2+ transport, namely ruthenium red, an inhibitor of the Ca2+ uniporter (the normal influx ro...

The characteristics of Ca2+ release in relation to Ca2+ binding were studied in sarcoplasmic reticulum vesicles isolated from canine myocardium. The Ca2+ binding appeared to be dependent on ATP as a 4 fold increase in Ca2+ binding was observed upon the addition of ATP. In the presence of a suboptimal ATP concentration (20 mumol/l; without ATP regenerating system) a rapid release of Ca2+ started...