QUANTITATIVE-DETERMINATION OF URINARY N-TAU-METHYLHISTIDINE OUTPUT AS AN INDEX OF MYOFIBRILLAR PROTEIN-DEGRADATION

  • 1 January 1981
    • journal article
    • research article
    • Vol. 89  (4) , 1155-1161
Abstract
N.tau.-Methylhistidine(3-methylhistidine) in urine of the rat is mainly derived from the degradation of actin and myosin in skeletal muscle, intestine and skin. The fractional degradation rates of the myosin-actin pools of these tissues were calculated from the time course of increase in the specific radioactivities of N.tau.-methylhistidine after daily administration of [methyl-14C]methionine to young adult rats under conditions of restricted food intake. The contributions to urinary excretion of N.tau.-methylhistidine from the 3 tissues were calculated from the fractional degradation rates and N.tau.-methylhistidine contents of the 3 tissues; 75.6% for skeletal muscle, 2.2% for intestine and 22.2% for skin. Skeletal muscle apparently is the major source of urinary N.tau.-methylhistidine output but the contribution of skin is not negligible in rats. The specific radioactivity of N.tau.-methylhistidine in urine was much higher than that of skeletal muscle. The fractional degradation rates of myosin and actin in skeletal muscle had similar values. Although the specific radioactivities of N.tau.-methylhistidine in myosin and actin were very different, the mean value was similar to that in mixed skeletal muscle.

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