Apelin-like immunoreactivity (Apelin-12 (Human, Mouse, Rat, Bovine) Antiserum, Catalog No.: H-057-23, Phoenix Pharmaceuticals) vascular endothelial cells of large conduit vessels. Photomicrographs show staining in saphenous vein (a) and coronary artery (c) with higher magnification of the respective vessels in (b) and (d).
Kleinz et al. Regul Pept. 2004 May 15;118(3):119-25. 

Immunocytochemistry Methods:
Cryostat cut tissue sections (10 Am for atrial and ventricular myocardium, lung, kidney and adrenal gland. 30 Am for saphenous vein, radial artery, left internal mammary artery and coronary artery) were left to dry overnight at room temperature. Tissue was fixed in ice-cold acetone for 10 min. Sections were incubated with 5% non-immunized swine serum in PBS for 1 h at room temperature to block nonspecific protein interaction. Tissues were incubated with rabbit-anti-apelin-12 (human/rat) antiserum at a dilution of 1:500 in PBS/T containing 1% non-immunized swine serum (1%SS PBS/T) for 72 h at 4^oC. Tissue sections were then washed three times for 5 min in cold PBS/T before the incubation with swine-anti-rabbit antiserum at a dilution of 1:200 in 1%SS PBS/T for 1 h at room temperature. After repeated washing, sections were incubated with rabbit peroxidase/anti-peroxidase complex at a 1:400 dilution in 1%SS PBS/T. Further washing preceded a 3-min incubation of tissue sections with a 2,5% solution of 3,3V-diaminobenzidine in 0.05M Tris-HCl buffer containing 0.3% hydrogen peroxide. The chromogenic reaction was stopped by immersing the slides in distilled water. Sections were dehydrated using a graded alcohol series before being submerged in xylene for 1 h to clear. Sections were mounted using DePeXGurr mounting medium and then examined using a standard light field microscope (Reichert-Jung, Austria).
Kleinz et al. Regul Pept. 2004 May 15;118(3):119-25.