Figure 7
From: Oxidative stress disruption of receptor-mediated calcium signaling mechanisms
Influence of tBHP on the concentration of calcium in the lumen of the ER. The relative level of [Ca2+]L was determined in cells in which cytosolic calcium had been depleted by permeabilization with 0.005% saponin. a Mag-Fura2 380/340 fluorescence ratio in a typical experiment. Saponin (0.005%) was added at the time indicated by the first arrow; carbamylcholine was added at the time indicated by the second arrow. Prior to permeabilization, the fluorescent signal associated with ER calcium is obscured by the dominant signal from cytosolic calcium. Data are the average from 20 cells in a typical experiment. [Ca2+]L was inferred from the average ratio measured between 100 and 110 sec. b The ratio of fluorescence intensity of Mag-Fura2 following excitation of at 380 and 340 nm was determined in control cells and in cells exposed to 1, 10 or 20 mM tBHP for 90 min prior to imaging, as indicated. This ratio is an indication of [Ca2+]L. The column and bars represent the mean and standard deviation from 3 experiments that involved separate determinations in 20 cells. The asterisks indicate a statistical difference from the control level as determined by ANOVA with a Tukey post-test.