Reproducibility of in vivo luminescence measurements on muscles after electrotransfer of a luciferase-encoding plasmid. Values are mean +/- SEM (n = 8 to 10) of the integrated values of luminescence in region of interest (ROI) of the tibial cranial muscle 7 days and 8 days after electrotransfer with 0.3 μg (white columns), 3 μg (clear grey columns) and 30 μg (dark grey columns) of pC1-luc into the tibial cranial muscle. Individual values are represented by black triangles and lines link values for the same muscles at day 7 and 8 after electrotransfer. For each amount of plasmid electrotransferred, luminescence values at day 7 (D7) and 8 (D8) did not differ. For both time of measurement (D7 and D8) a significant dose effect was observed. *** p < 0.001 between 0.3 and 3 μg (for groups D7 or D8). * p < 0.05 between 3 and 30 μg (for group D7 or D8). For all points, background luminescence was subtracted Inset: Linear correlation between values of luminescence measured at day 7 and 8 after electrotransfer. R2 = 0.92, p < 0.0001.