Figure 3.

(A) and (B) Quenching of fura-2 fluorescence at 360 nm by 200 μM Mn²⁺ in distal PVSMCs perfused with Ca²⁺-free KRB solution containing nifedipine (5 μM), but no CPA. (A) Time course of fluorescence normalized to fluorescence at time 0 (F/F₀) during normoxia (n=5 experiments in 134 cells) and hypoxia (n=5 experiments in 136 cells); (B) Mn²⁺ quenching, expressed as the percentage decrease in fluorescence from time 0, after Mn²⁺ administration in normoxia there was no significant difference with the spontaneous decrease in fluorescence measured in normoxic cells not exposed to Mn²⁺ (n=5 experiments in 141 cells, P>0.4), but in acute hypoxia, this rate was increased by approximate 2-fold (P<0.002). Quenching of fura-2 fluorescence at 360 nm by 200 μM Mn²⁺ in distal PVSMCs perfused with Ca²⁺-free KRB solution containing both nifedipine (5 μM) and CPA (10 μM); (C) Time course of fluorescence normalized to fluorescence at time 0 (F/F₀) during normoxia (n=5 experiments in 132 cells) and hypoxia (n=5 experiments in 129 cells); (D) Mn²⁺ quenching, expressed as the percentage decrease in fluorescence from time 0, was greater in cells exposed to hypoxia than that in normoxia (P<0.0001); (E) Effects of 50 μM SKF-96365 and 500 μM NiCl₂ on time course of fura-2 fluorescence at 360 nm normalized to values at time 0 before and after administration of MnCl₂ (200 μM) to hypoxic PVSMCs perfused with Ca²⁺-free KRB solution containing nifedipine (5 μM), but no CPA; (F) Average change in fura-2 fluorescence at 360 nm in hypoxic PVSMCs exposed to SKF-96365 (n=5 experiments in 126 cells), NiCl₂ (n=5 experiments in 131 cells), or vehicle control (n=5 experiments in 136 cells) at 10 min after administration of MnCl₂. * Significant difference from control (P<0.01); (G0 Effects of 50 μM SKF-96365 and 500 μM NiCl₂ on time course of fura-2 fluorescence at 360 nm normalized to values at time 0 before and after administration of MnCl₂ (200 μM) to hypoxic PVSMCs perfused with Ca²⁺-free KRB solution containing both nifedipine (5 μM) and CPA (10 μM); (H) Average change in fura-2 fluorescence at 360 nm in hypoxic PVSMCs exposed to SKF-96365 (n=5 experiments in 133 cells), NiCl₂ (n=5 experiments in 132 cells), or control (n=5 experiments in 129 cells) at 10 min after administration of MnCl₂. * Significant difference from control (P<0.0001).