Ntau-methylhistidine excretion is a valid index of myofibrillar protein breakdown in the guineapig (Cavia porcellus).
The recovery of radioactivity in the urine of guineapigs following a bolus intravenous dose of chromatographically pure 14C-Ntau-methylhistidine was measured in order to test whether the excretion of Ntau-methylhistidine (Ntau-MH) is a valid index of myofibrillar protein breakdown in these animals. Four male and four female guineapigs were dosed and after 7 days, 91.65+/-2.82% and 3.58+/-0.91% of injected radioactivity was recovered in the excreta and tissues, respectively. The average total recovery of 95.2+/-3.0% was not significantly different from 100%. Male guineapigs excreted the radioactivity more slowly than females (70% of the dose excreted within 74 h vs 39 h, respectively) but cumulative excretion at 7 days was the same for each sex. Chromatographic analysis of the urine showed almost all of the radioactivity to be associated with a single peak corresponding to Ntau-MH, indicating a lack of significant metabolism. These data show that although the clearance of 14C-Ntau-MH is slower than in rats or humans the urinary excretion of Ntau-MH is a valid index for myofibrillar protein degradation in the guineapig.
Rogers
P F
PF
Cooperative Research Centre for Tissue Growth and Repair, CSIRO Health Sciences and Nutrition, Adelaide BC, SA, Australia.
Tomas
F M
FM
D000199:Actins / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D005260:Female; D006168:Guinea Pigs / Q000652:urine*; D008297:Male; D008657:Metabolic Clearance Rate; D008762:Methylhistidines / Q000493:pharmacokinetics / Q000652:urine*; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D012727:Sex Characteristics
D000199:Actins; D002250:Carbon Radioisotopes; D008762:Methylhistidines; D009124:Muscle Proteins; D009218:Myosins