Brain polysomes and poly-U simulated protein synthesis in food restricted rats

Abstract

Effect of food restriction on (i) polysomal profiles (ii) distribution of 14C-phenylalanine and 3H-orotate into membrane bound ribosomes, free polysomes and monoribosomes, (iii) poly-U stimulated incorporation and (iv) the effect of pH-5 enzyme on the incorporation of phenylalanine by the ribosomes was investigated in the brain of rats from well (WF) and dietary restricted groups during the period of gestation alone (EI) and during the period of growth, gestation and lactation (EII). Polysomal profile showed a considerable lowering in the membrane bound ribosomes of EI and EII groups and free polysomes of EI group of rat brain compared with WF group. However, the membrane bound and free polysomes were higher in EII group compared with EI group. Monoribosomes decreased condiderably in the EII group compared with WF and EI group. Distribution of 14C-phenylalanine/mg protein was higher in the membrane bound ribosomes and monoribosomes in the brains of EI and EII groups and also in the free polysomes in EII group compared with WF group. Distribution of radioactive orotate/mg RNA was higher in all the three components of polysomal profile of EI and EII group brain compared with WF group but it was higher only in the monoribosomes of the EII group compared with EI group. Brain ribosomes from EI and EII groups responded more actively to the addition of poly-U than WF group. Synthesis of protein/synthesis of polyphenylalanine ratio (which roughly represents polysomes/monosomes ratio) showed lower polysomal content in the EII group brain compared with WF group. WF polysomes when incubated with EI or EII group pH-5 enzyme showed considerable increases in the incorporation compared with WF pH-5 enzymes. EI group polysomes when incubated with EII group pH-5 enzyme showed remarkable increase in the incorporation compared with WF and EI pH-5 enzyme. EII polysomes when incubated with any of the three pH-5 enzyme did not show any change. These results clearly demonstrate that brain polysomes are very sensitive to dietary restriction no matter at whatever physiological conditions they are exposed to this restriction.