Figure 3

Influence of exposure to tBHP on cholinergic receptor-mediated changes in cytosolic calcium. a Intracellular calcium levels were measured in CHO-M3 cells following exposure to the indicated concentration of tBHP for 90 min, a period which included the fura-2 loading incubation, and tBHP was continually present during the calcium measurements. Carbamylcholine (50 μM) was added at the time indicated by the arrows. Two effects of tBHP on the calcium responses were apparent: an increase in resting calcium concentration to > 100 nM and a decrease in the plateau (SOCE-mediated) response. The results are the average from 19–25 cells from a representative experiment; each experiment was performed 3–6 times with essentially similar results. b Exposure to tBHP for 90 min increased resting cytosolic calcium concentration. Each column and bar represents the mean and standard deviation from 10 experiments, each including separate measurements from 15–25 cells. Calcium concentrations were measured in the presence of normal a (2 mM) concentration of extracellular calcium. Exposure to 10 and 20 mM tBHP increased [Ca²⁺]_i compared to control cells (*, p < 0.05; ANOVA and Tukey’s test).