In vivo angiogenesis in normal and portal hypertensive rats: role of basic fibroblast growth factor and nitric oxide

Background: Angiogenesis plays a pivotal role in many processes. Here, we studied whether angiogenesis to basic fibroblast growth factor (bFGF) in normal and portal hypertensive rats requires nitric oxide (NO). Methods: To measure angiogenesis in vivo, two Teflon rings filled with collagen I (Vitrogen 100®) were fixed in the mesenteric cavity at day 0, with one supplemented with bFGF (100 ng). Portal hypertension was induced by partial portal vein ligation (PVL). Sham-operated rats served as controls (CON). The role of NO was tested by adding the NO formation antagonist Nω-nitro- -arginine (NNA; 3.3 mg/kg per day) to the drinking water. After 16 days, rings were explanted and embedded, and vessels were morphometrically counted. Results: bFGF significantly stimulated vessel formation per implant in CON rats (from 624±97 without stimulation to 1123±171, n=11, P<0.01), but not in PVL rats (from 1106±174 without stimulation to 1046±202, n=9). Without stimulation, numbers of ingrown vessels were significantly (P<0.05) higher in PVL compared to CON rats. NNA substantially inhibited angiogenesis in both groups (P<0.01). Vessel numbers were 202±124 for PVL (n=5) and 197±14 for CON (n=5) animals. bFGF did not reverse angiogenesis prevented by NNA (373±98 for PVL, 265±26 for CON, n=5 per group, NS). Conclusions: NO formation inhibition diminishes both unstimulated and bFGF-stimulated angiogenesis in CON rats. Moreover, bFGF cannot rescue NNA-inhibited angiogenesis in PVL rats.