Figure 2. Prostaglandin H₁ (PGH₁) stimulates Ca²⁺ mobilization from intracellular stores in CRTH2 transfectants and primary human eosinophils.

A–D: HEK293 cells stably expressing CRTH2 (CRTH2-HEK) were transiently transfected with a chimeric Gαqi5 protein to channel the Gi-sensitive CRTH2 receptor to mobilization of intracellular Ca²⁺. Cells were loaded with a Ca²⁺ fluorophore and CRTH2-specific Ca²⁺ traces were recorded over time upon challenge with the indicated agonists (A: PGD₂, B: PGH₁, C: PGH₂). A–C: representative data (mean + SEM of triplicate determinations. D: Maximum responses of all experiments were normalized to Ca²⁺ flux induced by 1 µM PGD₂ (mean + SEM, n = 3). E: PGH₁ induces Ca²⁺ mobilization in human eosinophils via CRTH2. Intracellular free Ca²⁺ levels were quantified by flow cytometry as described in the methods section. The level of Ca²⁺ mobilization in response to vehicle without agonist was set to 100%. Ca²⁺ mobilization upon addition of PGH₁, PGH₂, and PGD₂ is inhibited in the presence of 1 µM of the CRTH2 specific antagonist TM30089. Data are presented as the mean + SEM from 5 experiments conducted in triplicate, each experiment involving eosinophils from a separate donor.