Morphofunctional traits and reactivity of the portal vein

Abstract

Background: Portal vein is the most enigmatic vessel of our body because it regulates own contractile performances using a special pace-maker mechanism represented by cells of Cajal. The contribution of various metabolic mediators and natural vasotropic agents in the control of the portal blood circuit is much less studied compared to the arterial system in general and the hepatic system in particular. The studies designed on the structure, function, and reactivity of the portal vein in different preconditioning have brought some common but also distinct evidence of the arterial system. Nitric oxide production is higher partly due to reduced arginase expression, but muscular media is thinner. Periodic spontaneous contractions directed towards the liver gate are characteristic for portal vein (PV), and the longitudinal muscle fibers are considered to be responsible for this phenomenon. Spontaneous rhythmic oscillations of the cells of Cajal are triggered by increasing calcium ion concentration leading to their depolarization. PV constrictor effect of phenylephrine is dependent on the activity of receptors to ET-1. For PV is characterized the acetylcholine induced contraction either in vivo or in vitro, and this effect is thought to be dependent on ET-1. Conclusions: The establishment of main particularities of portal vein reactivity of action of different paracrine, endocrine, and hemodynamical stimuli represents an important tool for prediction of contractile disorders leading plausible to portal hypertension. Likewise, a well proven interplay between cholinergic and adrenergic stimulations and on the other hand between Ang II and ET-1 actions must be a support for pharmacological modulating of portal vein reactivity disorders.