FEEDING AND ARGININE DEFICIENT DIETS DIFFERENTIALLY ALTER FREE AMINO-ACID-CONCENTRATIONS OF HINDLIMB MUSCLE IN YOUNG-RATS

The objective of these experiments was to examine short-and long-term (7 d) effects of arginine-deficient diets on free amino acid concentra tions in hindlimb muscle of rats. In rats fed the control diet contain ing arginine (+Arg), muscle alanine and methionine concentrations were higher 1 and 2 h after feeding compared to food-deprived rats, wherea s branched-chain amino acids, arginine and asparagine concentrations w ere lower postprandially. In Experiment 1, rats were fed an arginine-d eficient (-Arg) diet with glutamate (+Glu) substituted for arginine; a lanine (+Ala), ornithine (+Orn) or citrulline (+Cit) were substituted for arginine in Experiment 2. In Experiment 1, arginine concentrations decreased in blood but not in muscle. This contrasts with rats fed -A rg/+Ala or -Arg/+Orn diets which had muscle arginine concentrations le ss than half the concentrations in controls or in rats fed the -Arg/+C it diet. Muscle essential amino acids in Experiment 2 did not differ b y diet, but muscle branched-chain amino acids were elevated relative t o controls in the rats fed -Arg/+Ala or -Arg/+Orn diets; how-ever, rat s fed the -Arg/+Cit diet had levels similar to the controls. Also, mus cle branched-chain amino acids were correlated with glutamine concentr ations in both blood and muscle. The measurements in the post-meal per iod suggest that muscle amino acid concentrations may more closely ref lect dietary amino acid patterns than do blood amino concentrations.