EFFECTS OF ACID LOADING ON SERUM AMINO-ACID PROFILES AND MUSCLE COMPOSITION IN NORMAL FED RATS

1. Impaired body growth, loss of lean body mass and negative nitrogen balance are common findings in chronic renal failure. Enhanced endogen ous protein catabolism in skeletal muscle induced by co-existent metab olic acidosis seems to be an important aetiological factor. 2. In urae mic patients abnormalities in blood amino acid profiles are present af ter a protein meal, suggesting impaired metabolism of ingested protein s. 3. This study demonstrates that acidosis induces changes in arteria l amino acid profiles in fed non-uraemic rats. These included increase d levels of threonine, histidine, proline, serine and glycine, and dec reased levels of tryptophan. These changes are similar to those found in uraemic patients after a protein meal, suggesting a pathogenic role of acidosis in the impairment of exogenous protein metabolism. 4. Int racellular amino acid levels in the muscle tissue partly reflect the c hanges in the extracellular level. 5. Acidotic animals had a decreased body weight gain and a reduced alkali-soluble protein/DNA ratio in mu scle cells compared with controls. 6. In conclusion, the results show that acidosis per se modifies the circulating amino acid profile in fe d rats, resulting in a pattern similar to the post-prandial amino acid changes described in uraemic patients. These abnormalities occur toge ther with impaired growth of skeletal muscle cells.