External and internal Ca²⁺ pools contribute to melanocyte dendritic Ca²⁺ transients. (A) Both removal of external₂ (no CaCl₂) and depletion of internal Ca²⁺ stores (+thaps) significantly reduce the number of dendritic Ca²⁺ transients in co-cultured melanocytes. n = 3 cultures per condition. Colors represent different skin donor. Significant by one-way ANOVA with post hoc Tukey means comparison (F[3,8] = 67.8, P < 0.00001, Tukey: all P-values < 0.01). (B–E) Distribution of the number of dendritic Ca²⁺ transients from co-cultures in A. (B) Before and after control treatment. (C) Before and after external CaCl₂ removal. (D) Before and after addition of 1 µM thapsigargin. (E) Before and after external CaCl₂ removal and addition of 1 µM thapsigargin. Colors in B–E correspond to conditions labeled in A.