Inositol phosphate-mediated Ca⁺⁺ flux activity in platelet PM.

(A) Na⁺/Ca⁺⁺ exchange activity of PM and inositol phosphate-mediated Ca⁺⁺ flux. The illustration shows kinetics of Na⁺/Ca⁺⁺ exchange and addition of either 10 μmol/L ionomycin (iono) or 50 μmol/L^1,4,5IP₃ (IP₃) at 10 minutes. All points are mean ± SEM of triplicate determinations, with similar results obtained in at least 2 other membrane preparations. (B) Dose–response relationship of ^1,3,4,5IP₄ (•) and ^1,4,5IP₃ (▿) induced Ca⁺⁺flux in plasma membranes.