2,4 dinitrophenol-uncoupling effect on ΔΨ in living hepatocytes depends on reducing-equivalent supply

Abstract

Mitochondrial uncouplers, such as 2,4 dinitrophenol (DNP), increase the cellular respiration by decreasing mitochondrial membrane potential (ΔΨ). We show that this respiratory effect can be transient or even prevented in isolated liver cells depending on the exogenous substrate used (dihydroxyacetone vs. octanoate or proline). Moreover the decrease in ATP/ADP ratio induced by DNP is partially restored by addition of octanoate or proline. By using rhodamine 123 (Rh123) monitored by flow cytometry in living hepatocytes, we were able to follow in time ΔΨ in such DNP-uncoupled cells in incubated with various substrates. The ability of this method to evaluate ΔΨ changes was assessed by using myxothiazol (3.6 μM), an inhibitor of the b-c1 complex of the respiratory chain which decreased ΔΨ (65%), or oligomycin (6 μg/ml), an inhibitor of the F0F1-ATPase which increased it (50%). Although DNP induced a dose-dependent decrease of ΔΨ, we found that octanoate or proline addition prevented such effect. We propose that octanoate or proline may counteract the uncoupling effect of DNP by providing a high supply of reducing equivalents to the respiratory chain.