Fig. (1) Calibration of fluorescence measurement in EGPE (a) and HT29 (b) cell lines. Labelled cells with Fluo-4,AM were incubated in medium 149 mM [Na+]o and 2.22 mM [K+]o, as described in material and methods. Control are labelled cells (Fluo-4,AM) with the addition of HBSS (--) instead calcium salt. Aliquots of 0.5 mM CaGluc2 was added, in samples (- -- -), as indicated in the figures, thin arrows, three times. When samples reach a plateau 9 µM ionomicin was added, in sample and control, gross arrow. Fluorescence values were obtained and expressed as Flourescence= [(Fl- Flmin)/ Flmin]. The Flmin is the last value of fluorescence obtained before calcium salt addition and Fl corresponds to the values obtained in each point of measure. Samples and controls run in duplicate and showed mean ± SD.