Electrolytes and free amino acids in leg skeletal muscle of young and elderly women.

Electrolytes and/or amino acids were determined in leg skeletal muscle biopsies from elderly (age range 57-75 years) and young (age range 20-35 years) apparently healthy women. When compared to the young group, the elderly one was characterized by increased levels of muscular Na+ and Cl-, while the calculated intracellular concentration of Na+ was reduced. The pattern and levels of free amino acids showed only minor differences between elderly and young women. Intracellular Mg2+ and K+ showed a significant correlation with muscle levels of simultaneously determined energy-rich phosphagen compounds that was published previously.