1. The present study aimed to demonstrate that interactions of cations hydrogen peroxied (H2O2) and the Na+-Ca2+ exchanger stimulate Ca2+ release and oscillations of cytosolic Ca2+[Ca2+]I in non-transfected Chinese Hamster Ovary (CHO) C1 cells and in transfected CHO (CK1.4) cells that contained an expression vector coding the Na+-Can2+ exchanger sequence. 2. The [45Ca2+] uptake assay, fura-2 fluorescence imaging and 2 2and 2 3 factorial orthogonal statistics provide compara-tive, direct, efficient, quantitative and transient methods to delineate the effects of such interactons on Ca2+ influx, Ca2+ release and [Ca2+]i in C1 and CK1.4 cells. 3. In contrast to the control of either Na2+-, Ca2+- or H2O2-free or C1 cells, ana elevated [45Ca2+] uptake was induced by Ca2+, Na+ and H2O2 individually and in combination, intra-cellular Ca2+ release was activated by H2O2 and by combinations of either H2O2 and Na+, H2O2 and the Na+-Ca2+ exchanger, Na+ and the Na+-Ca2+ exchanger or by H2O2, Na+ and the Na+-Ca2+ exchanger and a rise in [Ca2+]i was triggered by H2O2 Na+ and a combination of Na+ and the Na+-Ca2+ exchanger. 4. These results indicated that interactions between H2O2, Na+ and the Na+-Ca2+ exchanger stimulate intracellular Ca2+Na+ and the Na+-Ca2+ exchanger stimulate intracellular Ca2+ mobilization via Ca2+-induced Ca2+ release mechanisms, ATP-activated G-protein coupled P2y-purinoceptor-sensitive path-ways, Na+-Ca2+ exchanger-mediated Ca2+ influx and cation-π interaction (a strong non-covalent force between the cation and theπ face of an aromatic structure in the transmembrane protein). 5. The present findings, provide important clues for under-standing Ca2+ signal transduction mechanisms from the plasma membrane to the endoplasmic reticulum.