VEGF121- and bFGF-induced increase in collateral blood flow requires normal nitric oxide production
The angiogenic proteins basic fibroblast growth factor (bFGF; FGF-2) and vascular endothelial growth factor 121 (VEGF121) are each able to enhance the collateral-dependent blood flow after bilateral femoral artery ligation in rats. To study the effect of nitric oxide (NO) synthase (NOS) inhibition on bFGF- or VEGF121-induced blood flow expansion, the femoral arteries of male Sprague-Dawley rats were ligated bilaterally, and the animals were given tap water [non- NG-nitro-l-arginine methyl ester (l-NAME) group; n = 36] or water that contained l-NAME (l-NAME group; 2 mg/ml, n = 36). Animals from each group were further divided into three subgroups: vehicle ( n = 12), bFGF (5 μg · kg−1· day−1, n = 12), or VEGF121(10 μg · kg−1· day−1, n = 12). Growth factors were delivered via intra-arterial infusion with osmotic pumps over days 1–14. On day 16, after a 2-day delay to permit clearance of bFGF and VEGF from the circulation, maximal collateral blood flow was determined by85Sr- and141Ce-labeled microspheres during treadmill running.l-NAME (∼137 mg · kg−1· day−1) for 18 days increased systemic blood pressure (∼26%, P < 0.001). In the absence of l-NAME, collateral-dependent blood flows to the calf muscles were greater in the VEGF121- and bFGF-treated subgroups (85 ± 4.5 and 80 ± 2.9 ml · min−1· 100 g−1, respectively) than in the vehicle subgroup (49 ± 3.0 ml · min−1· 100 g−1, P < 0.001). In the presence of NOS inhibition byl-NAME, blood flows to the calf muscles were essentially equivalent among the three subgroups (54 ± 3.0, 56 ± 5.1, and 47 ± 2.0 ml · min−1· 100 g−1in the bFGF-, VEGF121-, and vehicle-treated subgroups, respectively) and were not different from the blood flow in the non-l-NAME vehicle subgroup. Our results therefore indicate that normal NO production is essential for the enhanced vascular remodeling induced by exogenous bFGF or VEGF121in this rat model of experimental peripheral arterial insufficiency. These results imply that a blunted endothelial NO production could temper vascular remodeling in response to these angiogenic growth factors.