Inhibition of cation channels in human erythrocytes by spermine.
In erythrocytes, spermine concentration decreases gradually with age, which is paralleled by increases of cytosolic Ca²+ concentration, with subsequent cell shrinkage and cell membrane scrambling. Cytosolic Ca²+ was estimated from fluo-3 fluorescence, cell volume from forward scatter, cell membrane scrambling from annexin V binding and cation channel activity with whole-cell patch-clamp in human erythrocytes. Extracellular spermine exerted a dual effect on erythrocyte survival. At 200 μM spermine blunted the increase of intracellular Ca²+, cell shrinkage and annexin V binding following 48 h exposure of cells at +37 °C. In contrast, short exposure (10-30 min) of cells to 2 mM spermine was accompanied by increased cytosolic Ca²+ and annexin binding. Intracellular addition of spermine at subphysiological concentration (0.2 μM) significantly decreased the conductance of monovalent cations (Na+, K+, NMDG+) and of Ca²+. Moreover, spermine (0.2 μM) blunted the stimulation of voltage-independent cation channels by Cl⁻ removal. Spermine (0.2 and 200 μM) added to the extracellular bath solution similarly inhibited the cation conductance in Cl⁻-containing bath solution. The effect of 0.2 μM spermine, but not the effect of 200 μM, was rapidly reversible. Acute addition (250 μM) of a naphthyl acetyl derivative of spermine (200 μM) again significantly decreased basal cation conductance in NaCl bath solution and inhibited voltage-independent cation channels. Spermine is a powerful regulator of erythrocyte cation channel cytosolic Ca²+ activity and, thus, cell survival.
Department of Physiology Institute I, Eberhard-Karls Universität Tübingen, 72076 Tübingen, Germany.
Yuliya V
YV
Kucherenko
Florian
F
Lang
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004594:Electrophysiology; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000037:antagonists & inhibitors*; D018408:Patch-Clamp Techniques; D013096:Spermine / Q000494:pharmacology*
D007473:Ion Channels; D013096:Spermine; D002118:Calcium