title: [Calcium binding by chemically stripped fibers of the rat myocardium during force development].
abstract: The aim of the study was to measure calcium binding by chemically skinned fibers of rat myocardium during force development at different concentrations of free Ca2+. Fiber fascicles were incubated in the solution with EGTA and 1% X-100 triton for 48 hours to achieve the maximal possible withdrawal of the sarcolemma and intracellular membrane structures. Ca2+ binding was determined using two markers. The fibers started developing a considerable isometric force at pCa 6.2-6.0, the maximal force was registered at pCa 5.0-4.8. At pCa 5.0 the fibers bound 3.59 +/- 0.21 nM of Ca/mg of protein, while at pCa greater than 6 less than one third of this amount was bound. When [Ca2+] was increased to over 1 microM the curve of Ca2+ binding became much steeper and coincided with the curve of force development. The results suggest that Ca2+ binding by myofibrils is evidently cooperative and depends on mechanic tension.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012996:Solutions; D013997:Time Factors
chemical_list: D012996:Solutions; D002118:Calcium
vernacular_title: Sviazyvanie kal'tsiia khimicheski skinirovannymi voloknami miokarda krysy vo vremia razvitiia sily.