Hepatic vascular response to anaphylaxis in isolated canine liver

We determined the vascular response to anaphylaxis in isolated canine livers perfused with autologous blood at a constant pressure via the portal vein, with hepatic artery ligation to simplify the vascular system. We also studied the validity of the double occlusion pressure (Pdo) as a measure of the capillary pressure (Pc) in the isolated canine liver. Pdo was compared with Pc measured using the traditional isogravimetric method (Pc,i), and both parameters showed a strong correlation (Pdo = 0.34 + 0.90 Pc,i; r = 0.93; P < 0.01). This indicated that Pdo provided an accurate indication of Pc in the isolated liver. In livers with anaphylaxis induced by the intraportal injection of Ascaris suum antigen (5 mg; 1.0 +/- 0.03 mg/kg body wt), hepatic vascular resistance and Pc (assessed as Pdo) were increased transiently by 29-fold and 3.4 mmHg, respectively, along with a significant increase of liver weight. The ratio of presinusoidal to postsinusoidal vascular resistance decreased from 0.89 +/- 0.05 to 0.36 +/- 0.12, suggesting that hepatic venous constriction was predominant. In livers perfused in the antidromic direction from the hepatic vein to the portal vein, anaphylaxis caused marked presinusoidal vasoconstriction that was consistent with hepatic venoconstriction as well as a significant and sustained decrease of liver weight below the baseline. These results suggest that anaphylaxis produced hepatic weight gain because of an increase in sinusoidal pressure caused by hepatic venoconstriction. Such hepatic venoconstriction may play an important role in the development of portal hypertension and hepatic congestion associated with anaphylactic shock.