Abstract
For assessing the nutritional and metabolic status in man, we have shown in man and animals that by measuring quantitatively excreted urinary modified RNA-catabolites the whole-body turnover of tRNA (from t6A, N6-threoninocarbonyladenosine), rRNA (from ψ, pseudouridine) and mRNA (from m7Gua, 7-methylguanine) can be estimated similarly as that of actin + myosin is determined from urinary m3His. Growing rats (41-54d) were fed either a control diet(C, 20 energy% as protein) or 1/2 c or 1/4 c, or they were given a low-protein (0-4 energy%) diet (LP) ad libitum. N-retention(NR): in control animals NR was 1-1.5g/kg/d. With C/2, NR briefly fell to O, then returned to ∼1g/kg/d. With C/4 NR was close to 0 for 3 days, then fell to -0.75gAg/d during days 4-5. With LP, NR dipped to -0.5g/kg/d and gradually returned to 0. Food restriction: in the C/4 group ψ and m7Gua increased within a day by 22-25%, then fell to normal (ψ) or subnoimal (m7Gua, -18%) levels until day 5. m3His was elevated by from day 2 onwards. We conclude that there was a rapid transient breakdown of ribosomes and mRNA followed by a longer lasting breakdown of actin and myosin. Protein restriction: with ip, m7Gua fell by ∼20% within a day and stayed near —25% (→day 14) while ψ started to decline on day 2, reached — 30% on day 5 and stayed there (→day 14). m3His was markedly increased only on days 2-3. These changes suggest the occurrence of an ordered sequence of efficient RNA and protein sparing mechanisms as an adaptation to protein deficiency.
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Schöch, G., Held, A., Topp, H. et al. 56 INRLLUEMCE OF FOOD RESTRICTION AMD OF LOW-PROTEIN DIET ON URINARY EXCRETION OF MODIFIED RNA CATABOLITES AND OF 3-METHULHISTIDINE (M3HIS) IN RELATION TO N-BALANCE IN GROWING RATS. Pediatr Res 24, 270 (1988). https://doi.org/10.1203/00006450-198808000-00082
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DOI: https://doi.org/10.1203/00006450-198808000-00082