Figure 8.

Both hypersensitivity and hyperreactivity of the TP receptors in hypoxic myocytes are normalized by exposure to milrinone. Hypoxic (HM) and normoxic (NM) myocytes loaded with fura-2AM were pre-incubated with 50 nM milrinone or diluent, then stimulated with serial concentrations of U46619 to derive concentration response curves. All curves presented as mean ± SD. (A) Milrinone had no effect on the maximal U46619 response in NM and (B) did not alter receptor sensitivity (NM EC₅₀ 1.3 µM, NM + milrinone EC₅₀ 1.4 µM, P = ns). (C) Milrinone attenuated the maximal Ca²⁺ response of HM to U46619 stimulation, and (D) decreased the sensitivity of the U46619 response curve (HM EC₅₀ 0.45 µM; HM + milrinone EC₅₀ 1.3 µM, P < 0.005; n = 6).