The effect of 1,25 dihydroxyvitamin D₃ on cell growth and colony formation from lin⁻c-kit⁺Sca-1⁺hematopoietic precursor cells. Fifty enriched hematopoietic precursors (lin⁻c-kit⁺Sca-1⁺) were added to wells containing media and cytokines (SCF, IL-6, IL-11, and Flt-3-ligand) and cultured with or without 1 μmol/L ATRA, 1 μmol/L 1,25 dihydroxyvitamin D₃ (D3), or 10 nmol/L D3 in the media. Cells were removed from liquid suspension after 7 days, washed, counted, and replated in semisolid medium without ATRA or D3. The cell counts (A) and total colonies (B) are given as the total number per 50 starting hematopoietic precursors. Results are shown from one experiment but are indicative of two separate experiments and are expressed as the mean ± SEM from 5 separate wells for each time point.