Effects of cycloheximide and changes in lighting regimen on the diurnal rhythm of rat liver protein synthesis

Abstract

Abstract Under standard conditions we have demonstrated a highly significant diurnal rhythmicity of translation for both total proteins and integral membrane proteins (IMPs) using a cell‐free system from rat liver. IMPs were prepared from microsomes by treatment with EDTA and 2 M LiCl. Normal rhythmic protein synthesis of untreated rats reaches a maximum at 03.00 h and an intermediate maximum at 12.00 h for both total proteins and IMPs. In the following experiments the animals were treated with cycloheximide (CHX) or were subjected to altered lighting regimens before hepatic protein synthesis was investigated in the in vitro system. Injection of CHX 4 hours prior to sacrificing the rats resulted in a marked modification of rhythmic translation, although CHX was washed out from the microsomal preparations and was not present during incubation. The maximal rate of translation was shifted from 03.00 h to 06.00 h, and the intermediate maximum was suppressed. The temporal shift of the maximum after CHX treatme...