Figure 7.

(A) Mitochondrial NADH was excited at 720 nm. (B and C) The identity of the signal was confirmed by an increase in response to the RC blocker cyanide (B) and a decrease in response to the RC uncoupler FCCP (C). (D through F) FAD²⁺ was excited at 458 nm (D), and reciprocal changes to NADH were observed in response to cyanide (E) and FCCP (F). Arrowhead, PT; arrow, DT. Bar = 20 μm. (G and H) Calibration of the NADH and FAD²⁺ signals with cyanide (maximally reduced state) and FCCP (maximally oxidized state) revealed that, in the resting state, mitochondria were more oxidized in PTs than DTs. Data are means ± SE per tubule from a total of 38 PTs and 29 DTs from five separate slices for NADH and 43 PTs and 42 DTs from four separate slices for FAD²⁺ (**P < 0.001).