FIG. 8.

Maximal production of IL-8 in Act-treated human intestinal epithelial cells (HT-29) requires calcium. HT-29 cells were stimulated with PBS or Act (12 ng/ml) for 8 h. BAPTA-treated cells (10 μM) were pretreated for 2 h before the addition of toxin. Supernatants were collected, ELISA for IL-8 was performed, and results are shown graphically. PBS alone or heated toxin (56°C/20 min) did not stimulate production of IL-8, whereas Act alone did induce production of IL-8 (1,106 pg/ml) by 8 h. BAPTA alone also induced low levels of IL-8 (192 pg/ml). As denoted by asterisk, pretreatment of cells with BAPTA significantly reduced Act-induced production of IL-8 compared to Act-treated cells alone.