Quantitative urinary excretion of unmetabolised N tau-[Me-C-14]methylhistidine by the common ringtail possum (Pseudocheirus peregrinus) Marsupialia

Six common ringtail possums (Psewbcheirus peregrinus) were intravenously injected with a standard dose of radioactive 3-Methylhistidine (N’-[Me-‘4C]MeH). The dose was rapidly and quantitatively excreted by the possums. More than 90% of radioactivity was recovered within 3 days. Thin layer chromatography and mass spectroscopy showed that 97% of recovered radioactivity was associated with unmetabolised N’-[Me-14C)MeH. These data satisfy two key requirements for the validity of urinary 3-Methylhistidine (Nr-3MeH) excretion as an index of muscle protein catabolism in P. peregrinus.