TPO evokes calcium flows in cultured Mks. (A) In physiological Ca²⁺ concentration (1.5 mM), chronic exposure to rhTPO (10 or 50 ng/mL) evokes Ca²⁺ spikes in mature Mks whereas starvation from rhTPO did not elicit any Ca²⁺ spike. The statistical analysis of peak fluorescence intensities is shown by box plot depicting the upper and lower values (lowest and highest horizontal line, respectively), lower and upper quartile with median value (box), and outside values (dots). Overall, data derives from 266 measurements from 4 independent experiments (P < .05). (B) In physiological Ca²⁺ concentration (1.5 mM), 10 minutes of stimulation with rhTPO (100 ng/mL) evokes an initial rise in [Ca²⁺] followed by a plateau that is lowered in the absence of extracellular Ca²⁺ (Ø Ca²⁺) and completely abolished by [Ca²⁺]_i chelation by BAPTA-AM. (C) Statistical analysis of peak and plateau fluorescence intensities in Mks treated as in panel B. The statistical analysis of peak fluorescence intensities is shown by box plot depicting the upper and lower values (lowest and highest horizontal line, respectively), lower and upper quartile with median value (box), and outside values (dots). Overall, data derive from 207 measurements from 3 independent experiments.