OBJECTIVE To gain some insight on the lesser arrhythmogenic properties of PST2744 [(E,Z)-3-((2-aminoethoxy)imino)androstane-6,17-dione hydrochloride] compared with digoxin, we compared modulation of intracellular Ca2+ dynamics by the two agents. METHODS SERCA (sarcoplasmic reticulum Ca2+-ATPase) activity and Ca2+ leak rate were measured in sarcoplasmic reticulum (SR) vesicles from guinea pig ...

We have examined the Ca2+ content and pathways of Ca2+ transport in frog rod outer segments using the Ca2+-indicating dye arsenazo III. The experiments employed suspensions of outer segments of truncated, but physiologically functional, frog rods (OS-IS), intact isolated outer segments (intact OS), and leaky outer segments (leaky OS with a plasma membrane leaky to small solutes, but with sealed...

The properties of Na-Ca-K exchange current through the plasma membrane of intact rod outer segments (ROS) isolated from bovine retinas were studied with the optical probe neutral red. Small cellular organelles such as bovine ROS do not offer an adequate collecting area to measure Na-Ca-K exchange currents with electrophysiological techniques. This study demonstrates that Na-Ca-K exchange curren...

We have examined the influence of different sterols and phospholipids on the activities of the cardiac sarcolemmal Na+-Ca2+ exchanger and Na+,K+-ATPase and the sarcoplasmic reticular Ca2+-ATPase in reconstituted proteoliposomes. When either the solubilized Na+-Ca2+ exchanger or the Na+,K+-ATPase is reconstituted into phosphatidylcholine (PC):phosphatidylserine (30:50 by weight) vesicles, high c...

To identify a rapid, uninhibited rate of exchange activity, we investigated in canine sarcolemmal vesicles the rapid kinetics of Na(+)-Ca2+ exchange. Sarcolemmal vesicles were incubated in 160 mM NaCl and 20 mM HEPES at 25 degrees C (pH 7.4) and actively loaded with 45Ca2+ for 2 minutes by Na(+)-Ca2+ exchange. After further uptake was inhibited by dilution into 0.15 mM Na(+)-free EGTA, sarcolem...

Na+-K+-ATPase and Na+/Ca2+exchange activities were studied in gills of Carcinus maenas in seawater (SW) and after transfer to dilute seawater (DSW). Carcinushyperregulates its hemolymph osmolarity through active uptake of Na+, Cl-, and Ca2+. In DSW total Na+-K+-ATPase activity in posterior gills quadrupled; Na+/Ca2+ exchange specific activity was unaffected, and total activity increased 1.67-fo...

The involvement of potassium ions in the Na(+)-Ca2+ exchange process was studied in rat brain synaptic plasma membrane (SPM) vesicles. Addition of equimolar [K+] to the intravesicular and the extravesicular medium led to a stimulation of the Na+ gradient-dependent Ca2+ influx; this stimulation was noticeable already at 0.5 mM and reached its maximum at 2 mM K+. The magnitude of the K+ stimulati...

Purified secretory vesicles isolated from bovine neurohypophyses were found to take up Ca2+ when incubated at 30 degrees C in media containing 10(-7) to 10(-4) M free Ca2+. At 10(-4) free Ca2+ 19 nmol/mg protein were taken up within 30 min. The initial uptake at this Ca2+ concentration was about 2 nmol/mg protein per min. The uptake of Ca2+ to secretory vesicles was not affected by ATP, oligomy...

Mace, Lisa C., Bradley M. Palmer, David A. Brown, Korinne N. Jew, Joshua M. Lynch, Jason M. Glunt, Todd A. Parsons, Joseph Y. Cheung, and Russell L. Moore. Influence of age and run training on cardiac Na / Ca2 exchange. J Appl Physiol 95: 1994–2003, 2003. First published July 25, 2003; 10.1152/japplphysiol.00551.2003.— Effects of age and training on myocardial Na /Ca2 exchange were examined in ...

Removal of external Ca2+ facilitated endogenous taurine release in cultured rat astrocytes. The stimulated release was not affected by furosemide, sucrose, tetrodotoxin and 3,4-dichlorobenzamil, but partially inhibited by nifedipine. Omission of external Na+ increased basal taurine release, and the effects of Na+ removal and Ca2+ depletion on the release were additive. The Na(+)-free condition ...