Means of neo-synthesized 15-Keto PGE₂ on PGE₂ are represented for 5 × 10⁶ cells after 1 and 2 weeks of culture in the ( ) presence or (□) absence of 1,25-(OH)₂D₃ (10⁻⁸ mol/L). Experiments were performed on three different neonatal blood samples.