L-ARGININE DOES NOT IMPROVE ENDOTHELIUM-DEPENDENT RELAXATION IN IN-VITRO WATANABE RABBIT THORACIC AORTA

The findings that even a single in vitro addition of L-arginine is abl e to normalize endothelium function in cerebral vessel from diet-induc ed hypercholesterolemic rabbits prompted us to investigate if similar results could be obtained on Watanabe rabbits thoracic aorta, in which we previously demonstrated low content of the amino acid. L-Arginine (1 mM) preincubated for 45 minutes before the addition of drugs for st uding endothelium-dependent vascular relaxation, did not modify the ef fect of acetylcholine on aortic isolated preparations. The lack of any effect by L-arginine indicates that the amino acid deficiency is not main cause of the impairment of endothelium function. The muscarinic r eceptor functionality affected by atherosclerotic process and/or the i ncreased synthesis of EDCFs could account for the reduced endothelium- dependent relaxation.