IL-3 does not inhibit ALP levels in osteoblastlike cell lines MC3T3-E1 and C2C12 and increases cell number in primary murine cultures. (A) MC3T3-E1 or C2C12 cells were treated with 50 ng/mL BMP-2 to stimulate OBL differentiation and increasing concentrations of IL-3 (0.1 to 10 ng/mL). ALP levels measured at 10 days were corrected for protein content, and are represented as percent control cultures (without BMP-2 stimulation). (B) Cell number in primary murine cultures was determined by the MTT assay after a 10-day culture of primary OBL cells with or without the addition of IL-3. Low concentrations of IL-3 (0.01 to 0.1 ng/mL) did not decrease cell number. High concentrations of IL-3 (more than 1 pg/mL) increased cell number. Data are represented as average ± standard deviation for 4 wells for each concentration and are representative of 3 independent experiments. ^*P < .05.