Ion-exchange chromatography of amino acids in sweat collected from healthy subjects during sauna bathing.

Amino acids were measured by ion-exchange liquid chromatography in sweat samples obtained from 22 healthy men during sauna bathing. Amino acids were also measured in plasma (collected before breakfast) and urine (24-h collections) from the same subjects. Serine, ornithine, citrulline, and aspartic acid were present in sweat in mean concentrations >10-fold their mean concentrations in plasma. In contrast, glutamine, cystine, α-aminobutyric acid, and α-aminoadipic acid were present in sweat in mean concentrations that were <0.2 times their mean concentrations in plasma. Concentrations of specific amino acids in sweat bore no apparent relationship to their concentrations in urine. Thus, citrulline was abundant in sweat, whereas only traces of citrulline were found in urine. Conversely, glutamine, taurine, cystine, and several other amino acids were abundant in urine but were present in very low or undetectable concentrations in sweat samples. This study indicates that the physiological mechanisms controlling excretion of amino acids in sweat differ fundamentally from those regulating renal excretion of amino acids.