ATRA reduces the proliferation rate of mast cells under stimulation with SCF.

The 5 × 10⁴ 10-week cultured mast cells were incubated in the presence or absence of SCF at 100 ng/mL for 1 week. ATRA was used at 10⁻⁷ mol/L. (A) The viable cells were enumerated every day. SCF alone, open circles; SCF+ATRA, closed circles; no factors, open squares; ATRA alone, closed squares. (B) The DNA distribution was examined by labeling of the cells with PI on day 2. FSC, forward light-scatter characteristics; SSC, side-scatter characteristics.