Relationship between Rates of Hepatic Protein Synthesis, Cyclic AMP Content and Phosphorylation of Ribosomal Proteins

Summary

The administration of glucagon in vivo to rats (200 μg i.P.) brings about a 40 percent inhibition of hepatic bulk protein synthesis. This inhibitory effect is the result of a preferential action of the hormone, decreasing the rate of the polypeptide chain elongation step. The possibility that cAMP was a mediator of this effect was investigated on the basis of previous observations demonstrating a good correlation between the metabolic effects of glucagon and the hepatic cAMP content and also taking into account the inhibitory effect of cAMP on protein synthesis in cell free systems. Under our experimental conditions a positive correlation between the inhibition of hepatic protein synthesis mediated by glucagon, cAMP content and degree of phosphorylation of ribosomal proteins does not seem to exist. This finding suggests that, in contrast to other metabolic events, the inhibition of hepatic protein synthesis induced by glucagon is mediated by factor(s) other than cAMP.

Key-Words:

Glucagon - Hepatic Protein Synthesis - Hepatic cAMP - Ribosomal Proteins Phosphorylation