Freie und Membrangebundene Ribosomen in der Rattenleber: Tagesrhytmik und hormonale Einflüsse / Free and Membrane-bound Ribosomes in Rat Liver: Daily Rhythm and Hormonal Influences

Abstract

Free and membrane-bound ribosomes were isolated from rat liver and quantitized by photometric methods. The amount of membrane-bound ribosomes remaines relatively constant over 24 hours whereas the amount of free ribosomes changes considerably: a maximum appears between 6-9 h, a minimum between 18-21 h. Fasting the animals increases the overall variance. Injections of cortisol 4 hours before killing the animals increases the total amount of ribosomes and induces a definite maximum of membrane-bound ribosomes at 6 h. The maximum of free ribosomes appears at the same time as in control animals. In contrast to cortisol, corticosterone has no effect on the total amount of ribosomes, it induces, however, a maximum of membrane-binding between 18-21 h. Also in this case the maximum of free ribosomes remains unchanged. In the evening, the protein content of free ribosomes decreases whereas a change was not observed in membrane-bound ribosomes. Cortisol increases the protein content in free and membrane- bound ribosomes.