Key result
In conscious rats with cirrhosis, NG-monomethyl-L-arginine decreased cardiac output by 35% and reduced portal pressure from 15.3 to 13.6 mm Hg, indicating normal NO-mediated vasodilator tone.
Why the study?
Does nitric oxide synthesis inhibition alter hemodynamics differently in cirrhotic rats compared to normal rats?
Does nitric oxide synthesis inhibition alter hemodynamics differently in cirrhotic rats compared to normal rats?
The study provides evidence that nitric oxide-mediated vasodilatation is normal in rats with cirrhosis, challenging the hypothesis that NO synthesis is increased in portal hypertension.
Challenges increased-NO hypothesis in portal hypertension; leaves open relevance to human cirrhosis.
Because it has been hypothesized that the hyperkinetic circulation in portal hypertension is the result of increased synthesis of nitric oxide, we compared the hemodynamic effects of nitric oxide synthesis--specific agonist (L-arginine) and antagonist between normal and cirrhotic conscious rats. The dose-response curves showed that L-arginine significantly decreased arterial pressure and increased heart rate. These changes started at the 200 mg/kg dose and were similar in both groups of rats. In both groups of rats NG-monomethyl-L-arginine (25 mg/kg) significantly decreased cardiac output by 35%. In cirrhotic rats, NG-monomethyl-L-arginine decreased portal pressure from 15.3 +/- 0.9 mm Hg to 13.6 +/- 0.7 mm Hg and portal tributary blood flow from 7.8 +/- 0.7 ml.min-1.100 gm-1 to 5.9 +/- 0.7 ml.min-1.100 gm-1; it significantly increased portal territory vascular resistance from 950 +/- 108 dyn.sec.cm-5.100 gm-1 x 10(3) to 1,579 +/- 258 dyn.sec.cm-5.100 gm-1 x 10(3). In normal rats, portal tributary blood flow decreased similarly, by 27%, and portal territory vascular resistance increased by 55%. In neither group was hepatic arterial blood flow altered. Before and after NG-monomethyl-L-arginine administration, arterial cyclic GMP concentrations were not significantly different between normal and cirrhotic rats. In conclusion, this study shows evidence of a normal role for nitric oxide-mediated vasodilatation in rats with cirrhosis and that inhibition of nitric oxide synthesis reduces portal hypertension. These results did not support the hypothesis that nitric oxide synthesis is increased in cirrhosis.
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Sogni et al. (1992) studied Cirrhosis. NG-monomethyl-L-arginine and L-arginine vs. Normal rats was evaluated on Hemodynamic effects including cardiac output and portal pressure. In conscious rats with cirrhosis, NG-monomethyl-L-arginine decreased cardiac output by 35% and reduced portal pressure from 15.3 to 13.6 mm Hg, indicating normal NO-mediated vasodilator tone.
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