Table 2. Inhibitory effect of metformin on VO2 in permeabilized KB cells.
Permeabilization of KB cells was achieved after intact cells had been previously incubated for 30 min with or without 10 mM metformin. Digitonin was added to intact cells (see the Materials and methods section) in a medium containing 125 mM KCl, 20 mM Tris/HCl, 1 mM EGTA and 5 mM Pi/Tris (pH 7.2) at 37 °C. Permeabilized cells were then incubated in the presence of either 5 mM glutamate+2.5 mM malate or 5 mM succinate+0.5 mM malate+1.25 μM rotenone. VO2 was measured before and after the successive additions of 1 mM ADP/Tris, 0.75 μg/ml oligomycin, 0.5 μM CCCP, 3.8 μM myxothiazol and 1 mM TMPD+5 mM ascorbate. Myxothiazol-sensitive respiration was calculated and the results are expressed as means±S.E.M. (n=5 independent experiments, each performed in triplicate). *P<0.01 versus control.
| VO2 [nmol atoms O·min−1·(106 cells)−1] | ||||
|---|---|---|---|---|
| Glutamate/malate | Succinate/malate | |||
| Control | Metformin | Control | Metformin | |
| No addition | 1.5±0.1 | 1.0±0.1* | 2.4±0.2 | 2.4±0.2 |
| ADP | 5.0±0.2 | 2.6±0.2* | 7.5±0.3 | 7.7±0.4 |
| Oligomycin | 1.0±0.1 | 0.8±0.1 | 1.5±0.3 | 1.6±0.3 |
| CCCP | 6.1±0.5 | 3.9±0.3* | 8.2±0.6 | 8.4±0.6 |
| TMPD+a | 11.2±0.3 | 11.5±0.3 | 10.4±0.3 | 10.7±0.3 |