FIGURE 4.

Involvement of PI4P in supporting oscillations in [Ca²⁺]_i evoked by LTC₄. A, a typical control recording showing oscillations in [Ca²⁺]_i evoked by LTC₄ in the presence of external Ca²⁺. B, wortmannin (10 μm, 10-min pretreatment) accelerates rundown of the cytoplasmic Ca²⁺ oscillations. Rundown is less pronounced when PI4P (70 μm, 7-min pretreatment) is applied prior to stimulation. C, aggregate data from three independent experiments are compared. Each column represents data from >30 cells. ***, p < 0.001; ns, not significant. D, pretreatment with PI4P increases the cytoplasmic Ca²⁺ oscillation frequency. E, pretreatment with PI4P rescues oscillations in [Ca²⁺]_i in a cell pre-exposed to LiCl for 105 min. F, cytoplasmic Ca²⁺ oscillations evoked by LTC₄ are not rescued in LiCl-treated cells when the carrier for PI4P is used instead. G, PI4P fails to rescue oscillations in [Ca²⁺]_i in Li⁺-treated cells in the presence of BTP2. H, PI4P has no effect on the rundown of cytoplasmic Ca²⁺ oscillations in Ca²⁺-free solution containing 1 mm La³⁺ in a LiCl-treated cell. I, aggregate data comparing the number of Ca²⁺ oscillations over an 800-s recording period for the different conditions are shown. La³⁺ in 0 mm Ca²⁺ denotes 0 Ca²⁺ supplemented with 1 mm La³⁺. ****, p < 0.0001.