FIGURE 5:

Extracellular ATP degradation does not influence Ca²⁺ activation. Ca²⁺ activation measured by genetically encoded biosensor RGECO. (A) Addition of 200 µM ectonucleotidase inhibitor ARL67156 does not increase Ca²⁺ activation by ATP in MCF-10A cells. Error bars indicate SEM, n = 3. (B) Extracellular phosphate measurements after the addition of 10 µM ATP show no difference compared with 0 µM. Inset, phosphate standard curve. Error bars indicate SD, n = 3, p determined by t test. (C) Ca²⁺ activation by ATP decreases in the presence of the ATP scavenger apyrase (5 U). However, Ca²⁺ activation by the nonhydrolyzable ATP variant ATPγS does not decrease in the presence of apyrase. Error bars indicate SEM, n = 3.