INVESTIGATIONS OF THE FUNCTION OF THE VASCULAR ENDOTHELIUM IN PORTAL HYPERTENSIVE RATS

There were no differences between mesenteric arteries from sham or 14- day portal hypertensive (PH) rats in the potency of or maximum endothe lium-dependent relaxations (EDR) to acetylcholine. There were no diffe rences between sham-operated and PH rats in the effects of the combina tion of the nitric oxide synthase inhibitor N-G-monomethyl-L-arginine (100 mu mol/l) and methylene blue (10 mu mol/l) in causing a significa nt reduction in the EDR to acetylcholine. The degree of portal-systemi c shunting, as measured by Co-57-labeled microspheres, was unaffected by acute administration of N-G-monomethyl-L-arginine (50 mg/kg) or met hylene blue (5 mg/kg). In conclusion, nitric oxide is the main mediato r of EDR in rat mesenteric artery, and no evidence was found for an in creased role for endothelial-derived nitric oxide in PH rats.