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The effect of calcium-store depletion and refilling with various bivalent cations on tyrosine phosphorylation and Mn2+ entry in fura-2-loaded human platelets

1994; Portland Press; Volume: 303; Issue: 2 Linguagem: Inglês

10.1042/bj3030337

1470-8728

Stewart O. Sage, Richard W. Farndale, Stewart O. Sage,

Ion Channels and Receptors

To investigate the possible involvement of tyrosine phosphorylation in the process of store-regulated Ca2+ entry, ionomycin (in the presence of EGTA) was used to deplete the intracellular Ca2+ stores of fura-2-loaded human platelets, and the effect of refilling with Ca2+, Ba2+ or Sr2+ evaluated. Depletion of the intracellular Ca2+ stores resulted in an increase in protein tyrosine phosporylation. This increase is reversed when the stores were refilled in Ca2+ or Sr2+, but not Ba2+. Refilling of the stores with Ca2+ or Sr2+, but not Ba2+, suppressed Mn2+ entry. These findings support the hypothesis that tyrosine phosphorylation plays a role in mediating store-regulated Ca2+ entry in human platelets and provides evidence for tyrosine phosphatase activity regulated by the Ca2+ content of the intracellular stores.