Human cultured cells are widely used for the investigation of respiratory chain disorders. Oxidative properties are generally investigated by means of polarographic studies carried out on detergent-permeabilized cells.

By studying the oxidative properties of Epstein- Barr virus-transformed B lymphocytes, we found that the respiration was significantly decreased after 3-4 days of cell culture. Simultaneously, we observed decreased NAD(+)-dependent oxidations (malate, glutamate, pyruvate) that became dependent upon the addition of exogenous NAD+. The effect of NAD+ was shown to be related to an influx of catalytic amount of NAD+ into the mitochondrial matrix.

A full ability to oxidize NAD(+)-dependent substrates was restored less than 2 h after a change of the culture medium.

These observations suggested:

(a) the occurrence of fluxes of catalytic amounts of NAD+ through the mitochondrial inner membrane in human cells;
(b) an early control of mitochondrial metabolism by matrix NAD+ content in cells grown under limiting growth conditions;
(c) the possible confusion between complex I deficiency and a decrease content of matrix NAD+ when using human cultured cells.

About the Authors

Rustin P, Chretien D, Parfait B, Rotig A, Munnich A. (1997) Nicotinamide adenine dinucleotides permeate through mitochondrial membranes in human Epstein-Barr virus-transformed lymphocytes. Mol Cell Biochem. 1997 Sep;174(1-2):115-9.