The Relationship Between Prostacyclin Activity and Pressure in the Portal Vein

The effect of portal hypertension (induced by partial ligation) on the ability of the portal vein wall to produce prostacyclin (PGI₂) was studied in rats over a period of 6 weeks. PGI₂‐like activity measured by bioassay was shown to be significantly increased in portal vein segments during established hypertension when compared to control groups. As a collateral circulation developed with consequent fall in portal venous pressure, PGI₂‐like activity decreased. A positive correlation between PGI₂‐like activity and portal pressure has been demonstrated. Parallel measurements of this activity by bioassay and radioimmunoassay to 6‐keto‐prostaglandin‐F₁ α showed a positive correlation (r = 0.88) and suggested that PGI₂ is the inhibitory prostaglandin involved. The possible significance of these observations in relation to the hemorrhagic manifestations associated with portal hypertension in man is discussed.