Some factors which influence the amount of calcium stored at the superficially located sites in cardiac muscle cells.
The cell membranes of cardiac muscle cells are impermeable to the trivalent rare earth element, lanthanum (La3+). Because La3+ displaces Ca2+ from its binding sites and because it does not penetrate across the cell membrane, it can be used to determine how much Ca2+ is stored at these superficially located sites. Using this technique it has been possible to study the various factors which influence the Ca2+ storing capacity of these superficially located sites. Substitution of Cl- by NO3- and Br- in the bathing fluid, and prolonged periods of perfusion reduce, whereas hyperthyroidism, an increase in the extracellular concentration of Ca2+, and a reduction in the extracellular concentration of Na+ increase the amount of Ca2+ stored at these superficially located sites. Some drugs which are negatively inotropic (verapamil and pentobarbitone) reduce, whereas others, which are positively inotropic (ouabain), increase the amount of Ca2+ which is available for displacement by La3+. Ca2+ which is stored at these sites plays an important role in regulating cardiac contractility.
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001965:Bromides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D009566:Nitrates / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011817:Rabbits; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D001965:Bromides; D009566:Nitrates; D010042:Ouabain; D007811:Lanthanum; D014700:Verapamil; D002118:Calcium