title: Characterization of sarcoplasmic reticulum in skinned heart muscle cultures.
abstract: The plasma membranes of rat heart muscle, grown in cell culture, were made permeable with saponin in a Ca-free solution. The cells were then supplied with a medium resembling the cytosol, and the adenosine triphosphate (ATP)-dependent Ca2+ sequestration was measured in the presence of oxalate. The nonmitochondrial component accounts for about 50% of the total Ca2+ uptake. The nonmitochondrial accumulation of Ca2+ within myocardial cells was found to be reversible by addition of the Ca2+ ionophore A23187. On the other hand, the Ca2+ antagonist D-600 (50 microM) had almost no effect on Ca2+ accumulation. Caffeine reduced Ca2+ accumulation in the skinned cardiomyocytes in a concentration-dependent manner. In addition, the anticalmodulin drug trifluoperazine (TFP) reduced Ca2+ accumulation in the skinned cells. Because of the analogy between nonmitochondrial ATP-dependent Ca2+ accumulation and the sarcoplasmic reticulum (SR) function with regard to the influence of various agents, it is assumed that we actually measure Ca2+ accumulation in the SR. The rate of Ca2+ accumulation into the SR measured during the development of the cardiomyocytes in culture shows an almost linear increase as a function of culture age. Amiodarone, a potent antiarrhythmic agent, and its metabolite, desethylamiodarone, inhibited Ca2+ accumulation into SR, which may explain their therapeutic effect.
authors.affiliation: Otto Meyerhoff Drug Receptor Center, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
authors.forename: L
authors.initials: L
authors.lastname: Weinstein
authors.forename: H
authors.initials: H
authors.lastname: Brik
authors.forename: H H
authors.initials: HH
authors.lastname: Rotmensch
authors.forename: A
authors.initials: A
authors.lastname: Shainberg
mesh_terms: D000638:Amiodarone / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics; D002478:Cells, Cultured; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D012503:Saponins / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure*; D013696:Temperature; D013997:Time Factors; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D012503:Saponins; D014268:Trifluoperazine; D000001:Calcimycin; D002110:Caffeine; D000638:Amiodarone; D002118:Calcium