Endotoxin and the hyperdynamic circulation of portal vein—ligated rats

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Abstract
Humoral factors may be responsible for the hyperdynamic circulation seen in portal hypertension. Endotoxin, a peripheral arteriolar vasodilator, has been proposed to mediate this hemodynamic picture. We examined the pathogenic role of endotoxin in portal vein—ligated rats, a prehepatic portal hypertensive model with a well-developed hyperdynamic circulation. To this end, we (a) administered oral neomycin, a poorly absorbable antibiotic, at doses of 50 and 100 mg/day for 7 days and found no evident splanchnic hemodynamic effects of a 2-log—fold reduction of cecal aerobic bacterial flora as assessed by the radioactive microsphere technique in portal vein—ligated rats studied in the postanesthesia awake state; (b) assayed endotoxin in arterial samples using a quantitative limulus assay and found no evidence of endotoxinemia in PVL rats; (c) induced a state of endotoxin tolerance by repeated daily intraperitoneal injections of lowdose endotoxin and found no amelioration of the hyperdynamic state in portal vein—ligated rats. Our results do not support the hypothesis that endotoxin plays a major pathogenic role in the hyperdynamic circulation of this experimental model. (HEPATOLOGY 1990;12:1152-1156).