Figure 13.

Biphasic effect of (A): hydrogen sulfide (NaHS) or (B): L-cysteine (L-Cys) on mitochondrial oxygen consumption rate (OCR) in isolated rat liver mitochondria. Rat liver mitochondria were isolated and subjected to bioenergetic analysis using the Extracellular Flux Analysis method as described (Módis et al., 2013b). At lower concentrations, H₂S (0.1–1 μM) or L-cysteine (10–1000 μM) elicit a significant increase in mitochondrial activity, as evidenced by the measurement of two parameters, calculated ATP Turnover (state 3) and FCCP-stimulated Maximal Respiratory Capacity (state 3u). Higher concentrations of H₂S (3–30 μM) or L-cysteine (3000 μM) suppress mitochondrial activity. The right panels show representative experiments, depicting the effect of H₂S (1 μM, top panel) or L-cysteine (L-Cys, bottom panel). All experiments were conducted in the presence of 10 mM succinate. Data represent mean ± SEM of six experiments. *P < 0.05 and **P < 0.01 shows the effect of NaHS or L-cysteine, as compared to vehicle control (anova, followed by Tukey's test). Part A is reproduced with permission from Módis et al. (2013b). The animal experimentation component of the studies was conducted with the approval of the Animal Care and Use Committee (IACUC) of the University of Texas Medical Branch and according to the applicable guidelines of the National Institute of Health.