Characterization of voltage-dependent calcium influx in human erythrocytes by fura-2.
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.
Soldati
L
L
Nephrology, Milan University, S. Raffaele Hospital, Italy.
Spaventa
R
R
Vezzoli
G
G
Zerbi
S
S
Adamo
D
D
Caumo
A
A
Rivera
R
R
Bianchi
G
G
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
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