Borinate esters have dual effects on store-operated calcium entry. A. Cytosolic calcium concentration measurement of BL41 cells using indo-1 fluorescence. Cells were treated 10 min with TG 1 μM to allow Ca2+ release from ER and opening of SOC channels. After 10 min, 1 mM CaCl2 was re-added, allowing Ca2+ entry through SOC channels. Different 2-APB concentrations were applied 30 s prior to CaCl2. Error bars were omitted for clarity (maximum ~ ± 70 nM). B. Mn2+ quenching of indo-1 in BL41 cells stimulated by potentiating and inhibitory concentrations of 2-APB. Cells were pre-treated 10 min with TG 1 μM allowing Ca2+ release from ER and opening of SOC channels. 60 s after beginning of the recordings, 100 μM MnCl2 was added. At 120 s, potentiating concentration of 2-APB (10 μM) was added, followed 60 s later by inhibiting concentration of 50 μM. Fluorescence of indo-1 was recorded at 430 nm. Results expressed relative fluorescence prior to MnCl2 adding. C. 2-APB, DPBA and 2-ABB concentrations differently regulate SOCE of BL-41 cells. Experiments were done as in figure 1A, and peak [Ca2+]i was expressed as % of peak [Ca2+]i recorded in absence of any borinate ester compounds. Borinate ester compounds were added 30 s prior to CaCl2. D. Mn2+ quenching of indo-1 in BL41 cells stimulated by potentiating and inhibitory concentrations of DPBA. Same as in figure 2B, except that 3 and 50 μM DPBA were used. E. Mn2+ quenching of indo-1 in BL41 cells stimulated by potentiating and inhibitory concentrations of 2-ABB. Same as in figure 2B, except that 30 and 100 μM 2-ABB were used. F. Values of Indo-1 quenching in presence of the borinate esters were normalised to values obtained in the lonely presence of Mn2+ ions.