Fig. 6

IM-induced [Ca²⁺]_i increases after re-introduction of Ca²⁺. a IM (5 μM). Experiments were carried out using HCO₃ ⁻-containing solution. Addition of 5 μM IM induced a large transient increase in fura 2 fluorescence ratio (F ₃₄₀/F ₃₈₀) in Ca²⁺-free solution. Re-introduction of Ca²⁺ increased F ₃₄₀/F ₃₈₀, which plateaued within 3 min. The plateau level was extremely high. This increase was not inhibited by 1 μM Gd³⁺. b and c IM (1 μM, b) and TG (4 μM, c). Addition of 1 μM IM or 4 μM TG induced a small transient increase in F ₃₄₀/F ₃₈₀ in Ca²⁺-free solution. Re-introduction of Ca²⁺ induced a biphasic increase in F ₃₄₀/F ₃₈₀, which was inhibited by 1 μM Gd³⁺