Effects of Starvation on Rat Liver mRNA Translation Products

Abstract

The synthesis of rat liver protein and RNA decreases with starvation. It is not yet known whether such decreases are regulated strictly at a transcriptional level, or if post-transcriptional controls are also involved. In this study we investigate the effects of 0, 2, or 4 days starvation on the levels of specific, abundant mRNAs in total and polysomal RNA populations. The mRNAs were analyzed by translation in vitro in mRNA-dependent, cell-free, protein synthesizing systems. The resulting polypeptide products were separated by gel electrophoresis and visualized with fluorography. The amount of albumin translated from both polysomal and total cellular mRNA decreased 20-40% with fasting. In contrast, a specific peptide having a molecular mass of approximately 30 kDa increased two- to three-fold in total cellular RNA with a smaller increase observed in polysomal RNA. These changes were maximal at 2 days of starvation. Since starvation is known to cause alterations in liver metabolism the 30-kDa polypeptide may be related to enzymes or other proteins involved in this homeostatic response.