Relative arteriovenous potency of nitric oxide

ABSTRACT

Much interest has been focused on the role of endogenous and exogenous nitric oxide [NO] pathways as regulators of cardiovascular function in health and disease. Moreover, despite the well documented vasodilator effect of NO, the relative arteriovenous potency of nitric oxide donors and inhibitors and the role of NO in portal circulation remain unclear. So this study was designed to throw more light on the role of NO on different blood vessels in vitro. This work studied the effect of L-NAME, L-arginine,SNP and MB in 3 different doses on the contractile effect of submaximal dose of noradrenaline on isolated dog aortic,femoral artery,femoral vein and portal vein strips. L-NAME and MB induced a significant increase of noradrenaline induced contraction in all vascular strips with all tested doses. However the response of venous strips was significantly higher than arterial strips with the least effect on aortic strips and highest on portal vein strips indicating a higher sensitivity of veins especially portal vein and the importance of NO in maintenance of basal vascular tone in all tested strips. On the other hand L-arginine and SNP induced a significant reduction in the noradrenaline-induced contraction in all vascular strips with all tested doses. This effect was more in veins especially portal vein than arterial strips.This veno-selectivity illustrate a potential role for NO in control of venous tone and in turn preload which is a major risk factor in some cardiovascular diseases as heart failure.Also the high portal sensitivity under basal condition suggest a possible use of NO as therapeutic agents in portal hypertension, however further studies on portal hypertensive subjects are recommended to illustrate its effects under condition of increased portal pressure