title: Characterization of voltage-dependent calcium influx in human erythrocytes by fura-2.
abstract: Thus far, the methods used to determine erythrocyte Ca2+ influx have not allowed the assessment of the kinetics of ion uptake. To overcome this drawback, we studied a new method, using the fluorescent Ca2+-chelator fura-2, which directly quantifies intracellular Ca2+ changes in human erythrocytes. This method has the advantage over previous techniques that it monitors continuously cellular Ca2+ levels. The Ca2+ influx is modulated by cellular membrane potential in the presence of a transmembrane Ca2+ concentration gradient and exhibits a first slow increase of the intracellular Ca2+ concentration, followed, after the reachment of a threshold value of 125 +/- 13 nM Ca2+, by a faster increase until a plateau is reached. The influx rate is inhibited by dihydropyridines in the micromolar range. These findings support the hypothesis that erythrocyte Ca2+ influx is mediated by a carrier similar to the slow Ca2+ channels and is dependent on membrane depolarization.
authors.affiliation: Nephrology, Milan University, S. Raffaele Hospital, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Soldati
authors.forename: R
authors.initials: R
authors.lastname: Spaventa
authors.forename: G
authors.initials: G
authors.lastname: Vezzoli
authors.forename: S
authors.initials: S
authors.lastname: Zerbi
authors.forename: D
authors.initials: D
authors.lastname: Adamo
authors.forename: A
authors.initials: A
authors.lastname: Caumo
authors.forename: R
authors.initials: R
authors.lastname: Rivera
authors.forename: G
authors.initials: G
authors.lastname: Bianchi
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D004095:Dihydropyridines / Q000494:pharmacology; D004563:Electrochemistry; D004912:Erythrocytes / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D008564:Membrane Potentials; D011188:Potassium / Q000494:pharmacology; D013696:Temperature
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D005456:Fluorescent Dyes; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D002118:Calcium; D016257:Fura-2