Differente coinvolgimento dell’ossido d’azoto e della prostaciclina nella regolazione del tono vascolare sistemico e polmonare

In 14 anaesthetized and mechanically ventilated Large White pigs we analysed the involvement of nitric oxide (NO) and prostanoids in the regulation of systemic and pulmonary vascular tone. Endogenous release of NO was blocked by NG-nitro-L-arginine methyl ester (L-NAME 5 mg/kg i.v.), while prostanoids biosynthesis was blocked by indomethacin (3 mg/kg i.v.). The subsequent parameters have been evaluated: systemic (MAP) and pulmonary arterial pressure (MPAP), cardiac output (CO), heart rate (HR) and systemic (SVR) and pulmonary vascular resistances (PVR). Blocking NO increased MAP, MPAP and vascular resistances. These effects evidence that in pig the vascular tone is modulated by a continuous release of NO by endothelial cells. The block of prostanoids biosynthesis did not affect the vasoconstrictor effect of L-NAME on the pulmonary vascular bed, but strengthened its hypertensive effect on systemic one. Consequently these data show that systemic and pulmonary vascular tones are differently regulated.