Angiopeptin enhances acetylcholine-induced relaxation and inhibits intimal hyperplasia after vascular injury

The effects of the somatostatin analogue, angiopeptin (BIM-23014), on neoendothelial function, as evidenced by formation of prostaglandin (PG) I2 and by acetylcholine-induced relaxation (formation of endothelial-derived relaxing factor), were investigated in the rabbit aorta. A balloon catheter injury of the thoracic and abdominal aorta was induced in New Zealand White rabbits. Animals treated with angiopeptin for 2 or 4 wk were compared with untreated rabbits at 2 or 4 wk after the induction of injury, as well as to sham-operated controls. When the rabbits were killed, vascular rings were assessed for arachidonic acid-stimulated PGI2 formation, acetylcholine-induced relaxation, and the degree of intimal hyperplasia. Vascular rings from animals treated with angiopeptin exhibited enhanced acetylcholine-induced relaxation; however, angiopeptin treatment had no effect on arachidonic acid-stimulated PGI2 formation. Intimal hyperplasia in treated animals was reduced by 36%. Treatment with another somatostatin analogue, BIM-23030, did not enhance relaxation or inhibit intimal hyperplasia. These data suggest that treatment with angiopeptin may inhibit intimal hyperplasia in part by its beneficial effect on neoendothelial function.

Selective and complete blockade of acetylcholine-induced relaxation in rabbit aortic rings by N omega-nitro-L-arginine but not by glybenclamide

This study addressed the possibility that acetylcholine-induced relaxation in the rabbit aorta is mediated by dual mechanisms: one N omega-nitro-L-arginine (NLA)-sensitive, the other glybenclamide-sensitive. Acetylcholine, nitroglycerin and BRL38227 (lemakalim), an activator of glybenclamide-sensitive potassium channels, were added to an organ bath containing rabbit aortic rings in a cumulative manner in the absence or presence of NLA and/or glybenclamide. NLA inhibited acetylcholine-induced relaxation and potentiated the relaxant response to nitroglycerin. BRL38227 caused a dose-dependent relaxation in rabbit aortic rings, and 30 microM glybenclamide produced essentially complete inhibition of this relaxation. Glybenclamide alone produced no inhibition of acetylcholine-induced relaxation. These results indicate that glybenclamide-sensitive potassium channels in the rabbit aorta play no role in mediating the relaxant response to acetylcholine, while NLA can produce a selective and essentially complete blockade of the relaxant response to acetylcholine in the rabbit aorta.