Figure 4. Effects of hypoxia on mitochondrial membrane potential in type-1 cells.

Measurements of mitochondrial membrane potential were performed using rhodamine 123 (see Methods). A, original recording from a small type-1 cell cluster conducted in normal Tyrode. B, similar recording obtained in Ca²⁺-free Tyrode containing 100 μm EGTA. Hypoxia ranged from 5% O₂ down to anoxia. Note application of FCCP (1 μm) causes rapid increase in fluorescence as Rh123 is released from mitochondria due to depolarisation of ψ_m. Depolarisation is assumed to be complete in 1 μm FCCP. Effects of hypoxia were measured on a 0–100% scale where 0%= interpolated baseline fluorescence in 20% O₂ and 100%= interpolated maximum fluorescence in 1 μm FCCP. C and D, normalised summary data (mean ± SEM) from 11 recordings with best fit rectangular hyperbola (see Results for details) for normal Tyrode (C) and Ca-free Tyrode (D).