The molecules: mechanisms of arterial vasodilatation observed in the splanchnic and systemic circulation in portal hypertension.

A hyperdynamic splanchnic and systemic circulation is typical of cirrhotic patients and has been observed in all experimental forms of portal hypertension. The hyperdynamic circulation is most likely initiated by arterial vasodilatation, leading to central hypovolemia, sodium retention, and an increased intravascular volume. Arterial vasodilatation is regulated by a complex interplay of various vasodilator molecules and factors that influence the production of those vasodilator molecules. Nitric oxide (NO) has been recognized as the most important vasodilator molecule that mediates the excessive arterial vasodilatation observed in portal hypertension. The aims of this review are (1) to categorize NO synthase isoforms involved in NO overproduction; (2) to explain the mechanisms of endothelial NO synthase up-regulation; and (3) to summarize other molecules involved in the arterial vasodilatation.