Fig. 7. Overexpression of CPX I reduces nutrient-induced secretory function. (a) Western blot analysis of CPX I overexpression in INS1 cells. The transient transfection of CMV-CPX I increased CPXI expression. The effect of overexpression of CPX I was assessed on the secretory ability of INS1 (b) and ßTC3 cells (c) in response to glucose and KCl. Cells were transiently co-transfected with the plasmid encoding CPX I (CMV-CPX I) or the empty vector (CMV) and with the plasmid encoding hGH vector. The release of hGH under basal and stimulatory (20 mM glucose supplemented by forskolin and IBMX or 24 mM of KCl) conditions was measured by ELISA. In both INS1 and ßTC3 cells, overexpression of CPX I significantly decreased, by 50%, the amount of secreted hGH in response to glucose and to KCl compared to cells transfected with CMV. The figure shows the mean ± s.e.m. of at least three independent experiments measured in triplicate (***P<0.001).