FIGURE 3.

Apelin-13-induced cAMP and intracellular calcium accumulations are not affected by ser mutations. A, dose-response curve of cAMP accumulation for WT and mutational APJs. HEK293 cells expressing WT APJ or mutants were incubated for 20 min in 3-isobutyl-1-methylxanthine with various concentrations of apelin-13 (0.1–10,000 nm). Intracellular cAMP level was measured using the absorbance-based cAMP ELISA kits. Data represent four independent experiments. B, the variation of intracellular calcium fluorescence in 180 s. HEK293 cells expressing WT APJ or mutants were stimulated with apelin-13 (100 nm). The variation of intracellular calcium concentration was recorded by Fluo-4NW Calcium Assay Kits. Data represent four independent experiments.