Role of the adventitia in the cyclic GMP-mediated relaxant effect of Nω-hydroxy-L-arginine in rat aorta

N-omega- hydroxy- L - arginine ( L - NOHA), the stable intermediate of the nitric oxide synthase ( NOS)- catalyzed reaction, can induce NO/ cyclic GMP- dependent relaxation in the rat aorta, in an endothelium- and NOS- independent manner. In this study, the role of the adventitia in the endothelium- independent effect of L - NOHA was investigated. Despite a decrease in norepinephrine ( NE)- induced precontraction, adventitia removal in the rat aorta did not markedly alter the relaxant effect of forskolin, S- nitroso- N- acetylpenicillamine or glyceryl trinitrate. In contrast, both inhibition of NE- induced contraction and relaxation of NE- precontracted rings produced by L - NOHA were diminished in the absence of adventitia. Moreover, exposure to L - NOHA significantly enhanced the cyclic GMP level in the media of the aorta with, but not without adventitia. These findings demonstrate the role of the adventitia in the L - NOHA- induced decrease in tone and increase in cyclic GMP in the endothelium- denuded rat aorta. They suggest that NO or an NO- related compound formed from L - NOHA in the adventitia may produce paracrine effects. Copyright (C) 2005 S. Karger AG, Basel.