[Effect of tyrosine kinase and tyrosine phosphatase inhibitors on ATP- and thapsigargin-induced CA2+ entry in rat peritoneal macrophages].

The effect of two structurally distinct tyrosine kinase inhibitors, genistein (100 microM) and methyl-2, 5-dihydroxycinnamate (25 microM) on ATP- and thapsigargin-induced Ca2+ signals in Fura-2-loaded rat peritoneal macrophages was investigated. Both compounds were shown to inhibit ATP-evoked Ca2+ entry but not to release from internal stores. Both compounds also inhibit the store-dependent or "capacitative" Ca2+ influx stimulated by emptying the intracellular Ca2+ stores with endoplasmic Ca(2+)-ATPase inhibitor thapsigargin (100 nM). Genistein and methyl-2, 5-dihydroxycinnamate have no effect on Ca2+ release from intracellular stores. Tyrosine phosphatase inhibitor orthovanadate Na (50 microM) increases ATP-induced Ca2+ entry but does not prevent the inhibitory effect of genistein. These data are compatible with the role played by tyrosine phosphorylation in the control of Ca2+ entry in rat peritoneal macrophages.