Changes in the free and membrane-bound ribosomes in maternal rat liver during starvation

Free and membrane-bound ribosomal ribonucleic acid (RNA) from maternal rat liver was measured in virgin rats and in variously dated pregnant animals that were either fed or starved for one to four days. The total amounts of free and membrane-bound ribosomal RNA differed between pregnant and nonpregnant rats, but the free ribosomal RNA progressively decreased only in the nonpregnant animals. A similar conservation of membrane-bound ribosomal RNA was observed with starvation among the pregnant rats except for the very early dated pregnant rats. Radioisotope labeling experiments using 3H-labeled orotic acid demonstrated a slower increase in specific activity among fed rats, irrespective of pregnancy state. However, metabolic and physiologic changes associated with pregnancy imposed additional complicating factors to the study.