MATERIALS AND METHODS
Human B cell Burkit Lymphoma Raji cells (purchased from Pasteur Institute of Iran) were cultured in RPMI-1640 medium containing 10% calf serum. Then the cells were maintained at 37° C in a 5% CO2 air incubator and with passage every day. Cell culture was done under sterille conditions and below laminar-hood. With removal of Raji cells from flask stock through the use of trypan blue 0.4% in a suspension of Raji cells,viability was more than 97% (viability (%)= live cells/live cells and dead cells x 100).
The other steps were the removal of 75μl (15000 cell) from the suspension, transfering it to 96-well plates. Then 10μl of different Zn concentrations (10 nM -500μM) were added to all wells except the controls. Under below laminar-hood and sterille conditions, the plates were shaken and mixed well. Then the cells were maintained at 37° C in a 5% CO2 air incubator. At the end of incubation times (12- 72h), viability and cell proliferation were determined using both the trypan blue exclusion dye and MTT assay2. Also, cell morphology was evaluated by Wright-Gimsa staining.
Cytotoxic assay by MTT reduction
This was carried out using the MTTassay described by Mosmann et al (11). According to the test principles, the assay was based on the clevage of the tetrazolium salt (MTT), in the
presence of an electron coupling reagent,by active mitochondria.The water-insoluble formazan salt produced has to be solubilized in an additional step. Cells grown in a 96-well plate, were incubated with the MTT solution for approximately 4 hours. After the incubation period, a water-insoluble formazan dye was quantitaed using a spectorphotometer (ELISA reader).The revealed absorbance was directly correlated to the cell number.
Procedure
After the end-points of incubation time (12-72 hours) at 37° C and 5% CO2, the Raji cells were loaded with 10 freshly prepared and Millipore filtered MTT (5mg/ml PBS) and incubated for 4 hours at 25° C. After 4 hours of incubation to each well, 100 μl of isopropanol were added, and the O.D (optimal density) of product was evaluated in an ELISA reader at 540 nm wevelengh after 15 minutes (viability (%)=O.D. TESE/O.D. CONTROL X 100) (12,13).