Modulation of human erythrocyte Ca2+-ATPase activity by glycerol: the role of calmodulin.
The effect of an intracellular cryoprotectant glycerol on human erythrocyte Ca2+-ATPase activity and possible involvement of calmodulin in the regulation of Ca2+-pump under these conditions were investigated. The experiments were carried out using saponin-permeabilized cells and isolated erythrocyte membrane fractions (white ghosts). Addition of rather low concentrations of glycerol to the medium increased Ca2+-ATPase activity in the saponin-permeabilized cells; the maximal effect was observed at 10% glycerol. Subsequent increase in glycerol concentrations above 20% was accompanied by inhibition of Ca2+-ATPase activity. Lack of stimulating effect of glycerol on white ghost Ca2+-ATPase may be attributed to removal of endogenous compounds regulating activity of this ion transport system. Inhibitory analysis using R24571 revealed that activation of Ca2+-ATPase by 10% glycerol was observed only in the case of inhibitor administration after modification of cells with glycerol; in the case of inhibitor addition before erythrocyte contact with glycerol, this phenomenon disappeared. These data suggest the possibility of regulation of human erythrocyte Ca2+-ATPase by glycerol; this regulatory effect may be attributed to both glycerol-induced structural changes in the membrane and also involvement of calmodulin in modulation of catalytic activity of the Ca2+-pump.
Zemlyanskikh
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NG
Institute for Problems of Cryobiology and Cryomedicine, National Academy of Sciences of Ukraine, Kharkov, 61015, Ukraine. cryo@online.kharkov.ua
Kofanova
O A
OA
D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000097:blood*; D002147:Calmodulin / Q000097:blood*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D005990:Glycerol / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000097:blood; D012995:Solubility
D002147:Calmodulin; D003451:Cryoprotective Agents; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010710:Phosphates; C031938:calmidazolium; D000252:Calcium-Transporting ATPases; D005990:Glycerol