Regulation of Ornithine Decarboxylase and S-Adenosyl-L-Methionine Decarboxylase in Regenerating Rat Liver by Various Amines: Evidence for Translational Control.

Abstract

The activity of ornithine decarboxylase [EC 4.1.1.17] [OD] in regenerating rat liver could be completely or partially inhibited in vivo by 1 i.p. injection of various amines. Unphysiological, 1,3-diaminopropane depressed most effectively the activity of OD. It also depressed the activity of adenosylmethionine decarboxylase [EC 4.1.1.50] [AD], which was not inhibited by other amines. The activity of tyrosine aminotransferase was invariably stimulated by injection of the amines. Cycloheximide caused a rapid decay of the activity of liver OD (half-life 15 min) and also a decay of the activity of AD (half-life 36 min). 1,3-Diaminopropane inhibited the activity of OD (half-life 13 min) and to lesser extent also the activity of AD (half-life 120 min). .alpha.-Amanitin did not have any effect on the activity of the decarboxylases. These experiments are consistent with the view that diamines and spermidine might control the activity of OD in regenerating rat liver in vivo at steps beyond transcription. 1,3-Diaminopropane may similarly control the activity of AD suggesting that the synthesis of OD and AD may be coordinatively regulated in liver.