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Lymphoid Organ mRNA Translatability in Rats: Effect of Protein Energy Undernutrition in Early Life¹

Department of Nutrition, University of Montreal, Montreal, Quebec Canada H3C 3J7 ^* Johns Hopkins University School of Medicine, Baltimore, MD 21224

Synthesis of mRNA was studied in the spleen and thymus of rats that had been exposed to undemutrition early in life. To achieve this objective, lactating females were separated into two groups 1 wk after they gave birth to offspring. These control and experimental dams suckled 8–11 and 13–16 pups, respectively, for a period of 2 wk. The young of both groups were then killed, and their thymus and spleen were isolated. Polyadenylated RNA (poly A⁺ RNA) was fractionated by affinity chromatography on an oligo-dT-cellulose column. Poly A⁺ RNA content as well as the percentage of poly A⁺ RNA in relation to total RNA were both lower in the undernourished pups than in the controls. Analysis of the in vitro translation product primed by poly A⁺ RNA of the thymus and spleen revealed a rise in [³⁵S]methionine incorporation in the undernourished offspring, the increase being greater in the thymus than in the spleen. Sodium dodecyl sulfate polyacrylamide-gel electrophoresis, autoradiography and densitometric autoradiographic tracings confirmed these findings and demonstrated that proteins were synthesized at a higher level in the spleen and thymus of the undernourished rats than in the controls. These results show that undernutrition early in life could modulate the metabolism of mRNA and, consequently, protein synthesis in the lymphoid organs of rats. Furthermore, the data suggest that cell-mediated immunity as well as humoral immunity are both deranged in protein energy undernutrition.

KEY WORDS: • lymphoid organs • mRNA content • translatability • undernutrition • young rats

¹ This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada and by an institutional grant from the University of Montreal (CAFIR) awarded to U. S. Srivastava. Dr. G. M. Bhatnagar was supported by Grant #AM-31419 from the NIAMDD, NIH and by an institutional grant from the Johns Hopkins University, Baltimore, MD.

Manuscript received 19 February 1985. Revision accepted 2 September 1986.