Fig. (7) MTT activity after co-culture with Alhydrogel^® and USY. THP-1 cells were co-cultured with various concentrations of Alhydrogel^® or dealuminated zeolite Y (USY). At day 1 (■) and day 2 (▲) the number of cells in each of the incubations was counted and an MTT assay was performed. The MTT activity (absorbance) per 10⁶ cells was calculated and to normalize the samples, the ratio between MTT activity per cells in the various cell cultures and the results obtained from cells in culture medium without any further additions at the corresponding day was assessed. A. Cell number after culture with Alhydrogel^®. Cell number expressed as % of cells obtained after culture in medium without any further additions. B. Normalized MTT activity ratio of THP-1 cells cultured in the presence of Alhydrogel^®. Dotted line shows the expected normalized MTT ratio using the MTT assay to estimate the number of cells in a sample. C. Cell number after culture with USY. Cell number expressed as % of cells obtained after culture in medium without any further additions. D. Normalized MTT activity ratio of THP-1 cells cultured in the presence of USY. Data presented as mean +/- SD of three independent experiments.