title: Cellular origin of the rapidly exchangeable calcium pool in the cultured neonatal rat heart cell.
abstract: Calcium in the myocardial cell is highly compartmentalized and in the cultured neonatal rat heart cells over 66% of the exchangeable calcium exchanges extremely fast (t1/2 < 1 s). The goal of the present study was to investigate, in the intact cell, the locus of this pool. By comparing myoblasts and fibroblasts and their respective plasma membranes, it is concluded that in the intact myocyte a significant fraction of the large lanthanum displaceable calcium pool is attributable to intracellular components, not present in the fibroblast. At least 30% of the lanthanum displaceable pool resides intracellularly, as is shown with the use of the drugs nifedipine, ryanodine and thapsigargin. It is proposed that the diadic subsarcolemmal junctional region represents a significant locus for the pool.
authors.affiliation: Department of Physiology, UCLA School of Medicine.
authors.forename: J A
authors.initials: JA
authors.lastname: Post
authors.forename: G A
authors.initials: GA
authors.lastname: Langer
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D002451:Cell Compartmentation; D002478:Cells, Cultured; D007811:Lanthanum / Q000494:pharmacology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D013729:Terpenes; D012433:Ryanodine; D019284:Thapsigargin; D007811:Lanthanum; D009543:Nifedipine; D002118:Calcium