Figure 4. CRAC channels mediate Ca²⁺ entry in enamel cells.

(A) Ca²⁺dynamics in secretory stage enamel organ (SSEO) cells. SSEO cells were loaded with 5 μM Fura-2 AM and pretreated with Synta-66 (3 μM) (red traces) or left untreated (gray traces). Graphs represent means of [Ca²⁺]_i (in nM) calculated from the means of F340/F380 Fura-2 fluorescence ratios recorded in SSEO cells. SSEO cells were stimulated with thapsigargin (1.25 μM) to deplete ER stores resulting in an increase in [Ca²⁺]_i. Following readdition of extracellular Ca²⁺ (resulting in a final extracellular [Ca²⁺] of 2 mM), we observed a marked increase in [Ca²⁺]_i but in Synta-66 treated SSEO cells this [Ca²⁺]_i increase was significantly inhibited (p < 0.001, ANOVA). Panels B and C show delta peak (in nM) of ER- Ca²⁺ release and Ca²⁺ entry in control cells compared to Synta-66 pretreated cells Untreated SSEO cells analyzed: n = 16 (grey bars), Synta-66 pre-treated SSEO cells: n = 8 (red bars). ***(p < 0.001), ANOVA. (D) Ca²⁺ dynamics in maturation stage enamel organ (MSEO) cells. Experiments were conducted as described for panel A. Untreated MSEO cells (black traces), Synta-66 pre-treated MSEO cells (red tracings). MSEO cells stimulated with thapsigargin showed an increase in [Ca²⁺]_i. Following readdition of extracellular Ca²⁺ there was a marked increase in [Ca²⁺]_i but not in Synta-66 treated MSEO cells which was significantly inhibited (p < 0.001, ANOVA). Panels E and F show delta peak (in nM) of ER- Ca²⁺ release and Ca²⁺ entry in control cells compared to Synta-66 pretreated cells. Untreated MSEO cells analyzed: n = 14 (black bars); Synta-66 pre-treated MSEO cells analyzed: n = 8 (red bar). ***(p < 0.001), ANOVA.