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Department of Animal Science, North Carolina State University, Raleigh, NC 27695
The growth of peripheral tissues reflects the combined effect of endogenous and exogenous signals. Limits of endogenous signals are determined by genetics, which define a chronology of growth of individual tissues. Fractional synthesis rate of muscle also follows a chronology. Endogenous mediators are both systemic and local, with tissue response a product of combined effects. Exogenous signals derive from the environment and dietary intake. Exogenous somatotropin or ß-adrenergic agonists change endogenous genetic limits for protein deposition and change partition of absorbed amino acids by stimulating anabolic use of amino acids in peripheral tissues and decreasing catabolism. Peripheral tissues provide a valuable model to study the relationships between tissues and the complexity of in vivo regulation. Shifts in metabolism of nitrogenous compounds by the liver are an example of directed changes in nutrient partitioning that act to increase supply of amino acids to peripheral tissues in conjunction with a stimulus to increase anabolic amino acid use. Further studies should integrate tissue changes with intracellular mechanisms.
KEY WORDS: muscle liver hindquarters protein synthesis hindlimb nitrogen
1 Presented as part of the Nutrient Partitioning Minisymposium given at the Experimental Biology '93 meeting, New Orleans, LA, March 31, 1993. This minisymposium was sponsored by the American Institute of Nutrition and was supported by grants from Agway Inc.; Cargill, Nutrena Feed Division; Merck Research Laboratories; Monsanto Agricultural Co. and the National Pork Producers Council. Guest editor for this symposium was D. H. Beermann, Department of Animal Science, Cornell University, Ithaca, NY.