Ca2(+)-driven [3H]arachidonate release in electropermeabilized human platelets shows an absolute requirement for MgATP2-.

Addition of micromolar Ca2+ to electropermeabilized human platelets which had been pre-labelled with [3H]arachidonate causes release of 3H only when millimolar concentrations of a nucleoside triphosphate, e.g. ATP, are present in the incubation medium. Addition of millimolar Ca2+ in the absence of ATP, or preincubation with ATP before addition of micromolar Ca2+, fails to cause a significant increase in 3H release. Purine nucleotides are more effective than pyrimidine nucleotides in activating Ca2(+)-driven 3H release. This activation does not appear to involve phosphate transfer, since metabolically stable analogues of ATP, e.g. the beta gamma-imido analogue, are effective in promoting 3H release.