title: Calcium content of the erythrocytes: a sensitive and easy handling method for measuring free calcium ions, and modulation of the Ca2+ ion concentration by the calcium antagonists nifedipine and pentoxifylline.
abstract: 1. A method for determining free Ca2+-ions in the erythrocyte is described, using a commercially available ORION-Ca-electrode and calomel reference electrode assembly, where changes in free Ca2+-ion concentration upon addition of 0.01% digitonin could be measured. 2. The average value found for fresh cells from 20 healthy donors at 37 degrees C (pH = 7.4) was 0.20 +/- 0.04 mumol/L referred to a haematocrit of 10%. 3. Decrease of the simultaneously determined adenosinetriphosphate (ATP) concentration indicates that ATP is presumably needed to activate the Ca-ATPase. 4. In vitro addition of the calcium antagonists pentoxifylline and nifedipine, respectively, induced a normalization of the intraerythrocytic Ca2+-ion concentration after previous increase with the ion carrier ionophore A23187. 5. The advantages and possible clinical applications of this method are discussed.
authors.affiliation: Department of Pediatrics, University of Göttingen, Federal Republic of Germany.
authors.forename: E
authors.initials: E
authors.lastname: Friederichs
authors.forename: T
authors.initials: T
authors.lastname: Rädisch
authors.forename: H
authors.initials: H
authors.lastname: Winkler
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood* / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology*; D010431:Pentoxifylline / Q000494:pharmacology*; D013696:Temperature; D013805:Theobromine / Q000031:analogs & derivatives*
chemical_list: D007476:Ionophores; D000001:Calcimycin; D000255:Adenosine Triphosphate; D009543:Nifedipine; D013805:Theobromine; D010431:Pentoxifylline; D002118:Calcium