Genes expressed in Flk-1-positive endothelial precursors are expressed in endothelial cells of the ovary during angiogenesis. Immunofluorescence analysis on frozen ovary sections at 8 hours of the LP. Endothelial-positive cells were identified by staining with PECAM1 (green) antibody, and specific colocalization was valued by double staining with specific antibodies (red) as indicated. Colocalization analysis was performed with a confocal microscope. CL indicates corpus luteum. Scale bar, 40 μm.