Bacterial toxins and glucagon in liver cAMP regulation: a physiopathological role in liver diseases?

Alterations of the specific enzymes located in the cell membranes might promote changes of the cyclic nucleotides ratio which is regulatory in growth stimulation of hepatocytes. Bacterial toxins, hormones and drugs affecting cyclic nucleotides system can interfere with this process in liver diseases. The Authors have determined hepatic cAMP concentrations by means of cAMP radioimmunoassay, in vivo, in rats treated with cholera toxin (CT), E. coli endotoxin (LPS) and glucagon. CT (0.15 mg i.v./rat/4th hr) and glucagon (0.8 mg/i.v./10') (significantly p less than 0.01) increase liver cAMP from 1.72 n mol/g wet wt (controls) to 2.62 and 4.13 n mol/g wet/wt respectively. Serum transaminases levels were unmodified. LPS (1.5 mg/hg/i.v./3th hr) significantly (p less than 0.01) raises serum transaminase activity while liver cAMP was not affected. Kinetics study however show that LPS, at lower dosage (0.5 mg/hg i.v.) enhances liver cAMP before cytotoxicity is observed.