The effect of exogenous administration of glutamic acid (GL), aspartic acid (A) and glycine (G) on individual amino acids in the free amino acid pool was studied in skeletal muscles of 60- to 70-day-old normal (N) and dystrophic (D) mice. Both N and D mice received either 0.25 ml of saline (S) or 250 mg/kg weight of GL, A or G in 0.25 ml S subcutaneously for 13 days. GL, A, G or S did not cause any significant changes in the body and skeletal muscle weights of either group. Most of the individual amino acids were increased in skeletal muscles of GL-treated mice and were decreased in A- or G-treated animals compared to S administration in the N group. The picture was more dramatic in the D group: GL-induced amino acid elevations were more pronounced than the values of N- or S-treated D controls. A and G elicited amino acid increases in D mice compared to their S-treated counterparts. Most of the individual amino acids in skeletal of the D group were decreased relative to N mice after S, GL or A administration. This was evident when the D/N ratio was calculated for S, GL and A. The situation was very different after G administration since of the individual amino acids were augmented in the skeletal muscle of D mice compared to N animals.(ABSTRACT TRUNCATED AT 250 WORDS)