Kinetics of luminescence of tibial cranial muscle and knee joint after electrotransfer of a luciferase encoding-plasmid and either i.p. or local injection of luciferin. 3 and 60 μg of a plasmid encoding luciferase were electrotransfered into the left tibial cranial muscle and right knee joint respectively. Luminescence measurements were done 7 days after electrotransfer. Values are mean +/- SEM of the integrated values of luminescence in region of interest (ROI) of the knee joint or of the tibial cranial muscle. For all experiments, the first measurement was performed 2 minutes after luciferin injection. Panel A: i.p. luciferin injection (2.5 mg/250 μl), n = 5 Panel B: local luciferin injection into the muscle (100 μg/40 μl) and into the knee joint (50 μg/10 μl), n= 5/organ. Luminescence decreased with time in the muscle (t1/2 = 3.3 minutes), and in the knee joint (t1/2= 16.5 minutes).