Mitochondrial Membrane Potential in Lymphocytes as Monitored by Fluorescent Cation diS-C₃-(5)

Abstract

A lipophilic fluorescent cation diS-C₃-(5) and rotenone suppress the oxygen consumption rate of thymocytes in similar concentrations. Seventy percent inhibition corresponds to an inhibitor:cytochrome a molar ratio of about 1:1. Addition of uncouplers decreases the inhibition of respiration by diS-C₃-(5) (but not rotenone). FCCP in similar concentrations increases O₂ consumption in the absence of diS-C₃-(5) and the diS-C₃-(5) fluorescence intensity in the presence of TMPD in thymocyte suspensions.

In most thymoctye preparations, oligomycin (0.05–0.1 μg/mL) increases the fluorescence of diS-C₃-(5) and further addition of TMPD (50–100 μM) decreases the fluorescence.

Addition of NaCN (400 μM) after oligomycin leads to a fluorescence increase that is hardly affected by subsequent addition of 0.2 μM FCCP. Nigericin (10–50 nM) decreases the diS-C₃-(5) fluorescence.

The data indicate that the diS-C₃-(5) fluorescence associated with mitochondrial transmembrane potential (Δξ_m) may be an essential part of the diS-C₃-(5) fluorescence in lymphocyte suspensions. The changes of the diS-C₃-(5) fluorescence intensity in the presence of TMPD after FCCP addition reflect Δξ_m

Key Words:

• lipophilic cation
• optical probe
• diS-C₃-(5)
• mitochondrial membrane potential
• lymphocyte energetics
• mitochondria in cell