Fig. 4. Attenuation of illumination intensity increased the time to global depolarisation. (A,B) The rate of mitochondrial depolarisation was systematically slowed by attenuation of the illumination intensity by neutral density filters suggesting that ROS formation by fluorophore illumination was sensitising mPTP formation (P<0001, Kruskal-Wallis non-parametric ANOVA test, n=46, 27 and 38 cells imaged using 1%, 3.5% and 5% transmission filters, respectively).