Phosphorylation of lysine-rich histone in the isolated perfused rat liver. Effects of glucagon, cyclic adenosine 3':5'-monophosphate, and insulin.

The phosphorylation of lysine-rich (f 1) histone at a specific serine residue was studied in the isolated, perfused rat liver. Glucagon and adenosine 3’:5’-monophosphate stimulated phosphorylation at this site, confirming that the previously demonstrated stimulatory effect of these agents in intact rats was an effect directly on the liver. Insulin did not alter the phosphorylation of fl histone in the perfused liver. The stimulation by insulin previously observed in the whole animal, therefore, was an indirect effect, probably due to glucagon or catecholamines released in response to insulininduced hypoglycemia.