Effect of nebulized 25D and 1,25D on endothelial cell differentiation markers. 2 weeks of daily administration of different doses of 25D and 1,25D from postnatal day 0 to 14 resulted in significantly increased expression of VEGF (a) and FLK 1 (b) with all doses of 25D and 1,25D examined, except with 1000 ng/kg of 25D and 1 ng/kg of 1,25D. *p < 0.05 versus control (lower panels). Compared to the controls, increased expression of VEGF and FLK-1, with both 25D and 1,25D, was confirmed with immunofluorescence (representative images are shown in the top panels); n = 4