Vanadate changes Ca2+ influx pathway properties in human red blood cells.
The properties of the basal Ca2+ influx (measured using cells labelled with 45Ca2+) in intact human red blood cells (RBC) were compared with those of 45Ca2+ influx induced by vanadate. The basal Ca2+ influx was not sensitive to inhibitors of vanadate-induced Ca2+ influx such as the HS-reagent p-chloromercuribenzoate and low concentrations of Cu2+, and also the sensitivity to nifedipine was significantly weaker. High K+ known to suppress vanadate-induced 45Ca2+ influx had no effect on the basal Ca2+ influx. Both processes were saturated with Ca2+ but the latter was saturated at higher Ca2+ concentrations (KM(Ca) 2.1 vs. 0.5 mmol/l). These experiments favour the notion that vanadate changes the properties of the inward-directed Ca(2+)-transport pathway in human RBC membrane. Vanadate-induced 45Ca2+ influx was insensitive to pertussis toxin and cholera toxin, and several non-steroidal antiinflammatory agents did not influence it in a consistent manner. Li+ partly inhibited the 45Ca2+ uptake. Vanadate stimulated the incorporation of 32P(in) into PIP2 in human but not in pig RBC which are known to be defective in the phosphoinositide metabolism and in the vanadate-induced 45Ca2+ uptake. These results suggest that the change in the Ca2+ influx pathway properties induced by vanadate may involve changes in the metabolism of phosphoinositides but not of the arachidonate metabolism nor G-protein activation.
Varecka
L
L
Department of Biochemistry and Microbiology, Slovak University of Technology, Bratislava, Slovakia. varecka@checdek.chtf.stuba.sk
Peterajová
E
E
Sevcík
J
J
D000818:Animals; D016718:Arachidonic Acid / Q000097:blood; D002118:Calcium / Q000097:blood*; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D019204:GTP-Binding Proteins / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D007700:Kinetics; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000097:blood; D015398:Signal Transduction; D013045:Species Specificity; D013552:Swine; D014638:Vanadates / Q000494:pharmacology*; D020245:p-Chloromercuribenzoic Acid
D002729:Chloromercuribenzoates; D010716:Phosphatidylinositols; D016718:Arachidonic Acid; D014638:Vanadates; D020245:p-Chloromercuribenzoic Acid; D003300:Copper; D019204:GTP-Binding Proteins; D009543:Nifedipine; D002118:Calcium