Turnover in Muscles

The turnover rate of phosphatides is found to be increased in muscle of rats maintained on a diet deficient in fat (91). In the fasting mouse, all phosphatide fractions, with the exception of -cephalin, which remained constant, showed a large increase in rate of renewal and reached a maximum on the second day of fasting (93). 

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Chen HW. Role of cholesterol metabolism in cell growth. FedProc 1984 43 126-130. Dabrowski MR Peel WE, Thomson AE. Plasma membrane cholesterol regulates human lymphocyte cytotoxic function. Ear J Immunol 1980 10 821-827. Ostaszewski P, Kostiuk S, Balasinska B, Jank M, Papet 1, Glomot F. The leucine metabolite 3-hydroxy-3-methylbutyrate (HMB) modifies protein turnover in muscles of the laboratory rats and domestic chicken in vitro. J Anim PhysiolAnim Nutr (Swiss) 2000 84 1-8. 

Effect of Stimulation, Recovbey, and Glucose Administration on T Turnover IN Muscles of Cats in Postabsorptive State (151) ... 

Effect of Insulin on P Turnover in Muscles of Cats Fed Glucose (152) ... 

Figure 8.1 Body iron stores and daily iron exchange. The figure shows a schematic representation of the routes of iron movement in normal adult male subjects. The plasma iron pool is about 4 mg (transferrin-bound iron and non-transferrin-bound iron), although the daily turnover is over 30 mg. The iron in parenchymal tissues is largely haem (in muscle) and ferritin/haemosiderin (in hepatic parenchymal cells). Dotted arrows represent iron loss through loss of epithelial cells in the gut or through blood loss. Numbers are in mg/day. Transferrin-Tf haemosiderin - hs MPS - mononuclear phagocytic system, including macrophages in spleen and Kupffer cells in liver.

Phosphorus-31 MRS provides a valuable research tool to investigate the correlation between metabolic turnover and pathological fatigue in muscle such as asthenia and chronic fatigue s)mdrome (CFS). Jones et al. 

Axelsson, K. I., and Karlsson, J.-O. G. (1984). Nitroglycerin tolerance in vitro Effect on cGMP turnover in vascular smooth muscle. Acta Pharmacol. Toxicol. 55, 203-210. 

Androgen production falls with age in men and may contribute to the decline in muscle mass, strength, and libido. Preliminary studies of androgen replacement in aging males with low androgen levels show an increase in lean body mass and hematocrit and a decrease in bone turnover. Longer studies will be required to assess the usefulness of this therapy. 

Additional information <1-7, 11, 14, 15, 17-19, 21, 30> (<7> cell-free synthesis in mRNA-dependent rabbit reticulocyte lysate system [40] <2,4,5> high activities in tissues where turnover of energy from adenine nucleotides is great, e. g. muscle [3] <1-6,11,14,15> tissue distribution [3,46] <2,5> rabbit and human carry a minimum of 2 sets of isozymes within an individual one set in muscle, erythrocytes, brain and another in liver, kidney and spleen [3]) [3, 40, 46]... 

To meet these changing circumstances, the liver has remarkable metabolic flexibility. For example, when the diet is rich in protein, hepatocytes supply themselves with high levels of enzymes for amino acid catabolism and gluconeogenesis. Within hours after a shift to a high-carbohydrate diet, the levels of these enzymes begin to drop and the hepatocytes increase their synthesis of enzymes essential to carbohydrate metabolism and fat synthesis. Liver enzymes turn over (are synthesized and degraded) at live to ten times the rate of enzyme turnover in other tissues, such as muscle. Extrahepatic... 

There is no such clear cut difTcrcnlialiun as metamorphosis in the mammal, but development is an extremely complex process and has been shown to depend upon the presence of adequate amounts of thyroid hormones. Deficient development, especially of the central nervous system, is marked in ehildren suffering from thyroid deficiency early in life, ansi this inadequacy cannot be overcome completely by medication commenced after the first few weeks. In the adult, thyroxine is important in the maintenance of energy turnover in most of the tissues of the body, such as the heart, skeletal muscle, liver, and kidney, Other physiological functions, most notably brain aclivity and reproduction, are also dependent upon thyroxine, although the metabolic rales of the tissues concerned in these functions do not seem to be altered. 

Most of the iron in the body is in the form of haemoglobin in red blood cells and myoglobin in muscle. The remainder is in the liver, spleen and other tissues. Haemoglobin is essential for the proper functioning of every organ and tissue of the body. Iron has a rapid turnover rate in the chicken therefore, it must be provided in a highly available form in the diet on a daily basis. Iron deficiency can result in microcytic, hypochromic anaemia in poultry. Any internal infection such as coccidiosis can also interfere with iron absorption and lead to a deficiency. 

Arthur, P.G., M.C. Hogan, P.D. Wagner, and P.W. Hochachka (1992a). Modelling the effects of hypoxia on ATP turnover in exercising muscle. J. Appl. Physiol. 73 Til-160. 

Hochachka, P.W. and G.B. McClelland (1997). Cellular metabolic homeostasis during large scale changes in ATP turnover rates in muscles. J. Exp. Biol. 200 381-386. 

Rate of ATP Turnover in Rat Heart Muscle Rat heart muscle operating aerobically fills more than 90% of its ATP needs by oxidative phosphorylation. Each gram of tissue consumes 02 at the rate of 10.0 /xmol/min, with glucose as the fuel source. 

Each tissue, including the bloodstream, has a free amino acid pool. This amounts to a total of about 100 g. By far the largest fraction, 50-80%, is located in muscle. Kidney accounts for about 4%, liver for 10%, and the bloodstream another 4%. Glutamine and glutamate are major components of such pools. Free amino acid pools are in equilibrium with tissue protein. Tissue proteins are in a constant state of turnover, that is, biosynthesis and degradation from and to free amino acids. Only plasma proteins, which are largely synthesized in the liver, are not in equilibrium with the plasma free amino acid pool. 

Terjung, R. L. (1975) Cytochrome c turnover in skeletal muscle. Biochem. Biophys. Res. Commun. 66 173-8. 

Booth, F, W. (1977) Effects of endurance exercise on cytochrome c turnover in skeletal muscle. In The Marathon Physiological, Medical, Epidemiological, and Psychological Studies (Mllvy, P., ed.), pp. 431-439, Annals of the New York Academy of Sciences, Vol. 301, New York, NY. 

Changes in Protein Turnover in Anterior Latissimus Dorsi Muscles of Chickens During Stretch-Induced Hypertrophy... 

Laurent, G.J., Sparrow, M.P. 4 Mlllward, D.J. (1978) Muscle protein turnover in the adult fowl II. Changes in rates of protein synthesis and breakdown during hypertrophy of the anterior and posterior latissimus dorsi muscle. Biochem. J. 176, 407-417. 

There may be multiple metabolicpoolsofthe vitamin, with very different rates of turnover. In this case, short-term and long-term smdies will give very different estimates of the fractional rate of turnover of the total body pool. As discussed in Section 9.6.1, this is known to be a problem with vitamin Be, because some 80% of the total body pool is associated with muscle glycogen phosphorylase and has a much lower fractional turnover rate than the remaining 20%. 

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