title: Quantitative determination of urinary N-tau-methylhistidine output as an index of myofibrillar protein degradation.
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 three tissues were calculated from the fractional degradation rates and N tau-methylhistidine contents of the three tissues; 75.6% for skeletal muscle, 2.2% for intestine and 22.2% for skin. The results show that the skeletal muscle 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.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D006639:Histidine / Q000031:analogs & derivatives*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D008762:Methylhistidines / Q000378:metabolism / Q000652:urine*; D009132:Muscles / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D051381:Rats; D012867:Skin / Q000378:metabolism*
chemical_list: D000199:Actins; D008762:Methylhistidines; D006639:Histidine; D009218:Myosins; C028118:3-methylhistidine