The effect of melatonin treatment on respiratory states in isolated mitochondria from brown fat depots of control (untreated) and melatonin-treated ZDF and ZL rats. (A) The upper panel shows state 3, representing oxygen flux, while producing ATP in response to ADP pulses in the presence of substrates. (B) The lower panel illustrates state 4, or leak respiration, which shows oxygen flux in the absence of ATP synthesis. Glutamate/malate was used as the respiratory substrates. C, control; M, melatonin; ZL, Zücker lean rats; ZDF, Zücker diabetic fatty rats. Values are shown as mean ± SD. Superscript characters show significant differences determined by two-way analysis of variance (ANOVA) followed by the Tukey post hoc test (** p < 0.01, M-ZDF compared with C-ZDF rats; #
p < 0.05, C-ZDF compared with C-ZL rats).