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Neurons exposed to ammonia reproduce the differential alteration in nitric oxide modulation of guanylate cyclase in the cerebellum and cortex of patients with liver cirrhosis.

Rodrigo R, Erceg S, Felipo V

Laboratory of Neurobiology, Fundación Valenciana de Investigaciones Biomédicas, Amadeo de Saboya, 4, 46010, Valencia, Spain.

The activation of soluble guanylate cyclase by nitric oxide is increased in the frontal cortex but is reduced in the cerebellum of patients who died with liver cirrhosis. The aims of this work were to assess whether hyperammonemia is responsible for the region-selective alterations in guanylate cyclase modulation in liver cirrhosis and to assess whether the alteration occurs in neurons or in astrocytes. The activation of guanylate cyclase by nitric oxide was lower in cerebellar neurons exposed to ammonia (1.5-fold) than in control neurons (3.3-fold). The activation of guanylate cyclase by nitric oxide was higher in cortical neurons exposed to ammonia (8.7-fold) than in control neurons (5.5-fold). The activation was not affected in cerebellar or cortical astrocytes. These findings indicate that hyperammonemia is responsible for the differential alterations in the modulation of soluble guanylate cyclase in cerebellum and cerebral cortex of cirrhotic patients. Moreover, the alterations occur specifically in neurons and not in astrocytes.

Published 19 April 2005 in Neurobiol Dis, 19(1): 150-61.
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