Biomaterial Database

Spontaneous calcium release from sarcoplasmic reticulum. Assessment of other ionic influences. 1984

R D Mitchell, and P Palade, and S Fleischer

A form of spontaneous Ca2+ release from purified light sarcoplasmic reticulum has been recently described (Palade, P., Mitchell, R. D., and Fleischer, S. (1983) J. Biol. Chem. 258, 8098-8107). It is characterized by rapid Ca2+ efflux (1-10 mumol/min X mg protein) which begins only after a delay following preloading and depletion of extravesicular Ca2+. In the present study, the influences of a number of ionic factors modulating the spontaneous calcium release phenomenon are described. The divalent metal ions Mn2+ and Sr2+ and higher external [Mg2+] inhibit release. Mn2+ appears to inhibit from outside, whereas Sr2+ must be taken up to inhibit. Decreasing the phosphate concentration during preloading eliminates spontaneous release, but it can be partially restored with salts of other nonprecipitating anions. No such release was obtained with other Ca2+-precipitating anions, i.e. pyrophosphate, oxalate, and fluoride. The release characteristics are strongly dependent on the monovalent cation present. Spontaneous Ca2+ release is optimal at pH 6.8-7.0 and decreases sharply at higher and lower pH. Ca2+ release can be enhanced by addition, during the lag period, of concentrated salt solutions consisting of more permeant cations than anions, which may indicate that an inside positive membrane potential enhances the rate of calcium release. Spontaneous Ca2+ release can take place in the presence of sucrose, and Ca2+ efflux is not accompanied by a corresponding efflux of preloaded sucrose, demonstrating that the vesicles remain sealed during spontaneous release. The spontaneous Ca2+ release process is distinct from several other forms of Ca2+ release from sarcoplasmic reticulum.

UI	MeSH Term	Description	Entries
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012519	Sarcoplasmic Reticulum	A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.	Reticulum, Sarcoplasmic,Reticulums, Sarcoplasmic,Sarcoplasmic Reticulums
D013324	Strontium	An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.