Alterations in Cerebral Protein Metabolism in the Progeny of Protein-Calorie-Deficient Rats

Abstract

Beginning at days 8 or 14 of pregnancy, rats were fed either a 5 or 18% protein diet through the rest of gestation and all of lactation, and cerebral protein metabolism was evaluated in the progeny at various stages of development. On days 2, 10, 15, 21 postnatally, cerebral weight and cerebral contents of nucleic acids and proteins were higher in the young of adequately fed mothers than in pups raised in comparable litter sizes by malnourished mothers. In the former, cerebral weight, RNA, DNA and total protein increased by factors of 5.5, 4.5, 2.1 and 8.0, respectively, between days 2 and 21 compared with increases of 4.2, 3.6, 1.3 and 7.0 times for equivalent parameters in the malnourished rats. Developmental alterations in cerebral free amino acids were complex. Postnatal depressions in concentrations of alanine, glycine, phosphoethanolamine, taurine and ethanolamine were less marked in malnourished rats compared with the controls. The former showed more prominent age-dependent increase in γ-aminobutyric acid than the latter. Fast sedimenting ribosomal aggregates accounted for most of the cerebral ribosomes in both groups of rats. At day 10 postnatally, most of the ribosomes were recovered as free polysomes from control rats in contrast to findings in malnourished rats of the same age. At weaning, total polysome contents were similar in both groups and in vitro studies demonstrated no clear difference in ¹⁴C-leucine uptake. Nevertheless, protein synthesis as assessed in vitro was lower in malnourished cerebrum than in cerebral tissues from well-fed rats of comparable body and cerebral weights. There was also marked instability of cerebral mRNA-ribosome complex in control than in malnourished rats as evidenced by amounts of polysome disaggregation after in vitro incubation.