Determination of Uric Acid, Tyrosine, Tryptophan, and Protein in whole Human Parotid Saliva by Ultraviolet Absorption Spectrophotometry

Abstract

Intact undeproteinized samples of whole human parotid saliva were analyzed for uric acid, protein, tyrosine, and tryptophan by chemical and UV absorption technics. A simple rapid method has been devised for the simultaneous determination of uric acid, protein, tyrosine, and tryptophan in as little as 0.6 ml sample. The relation between the chemical (X) and spectrophotometric (Y) determinations for tyrosine is Y = 0.92 X + 0.09 with a correlation coefficient of 0.97. The fitted line for tryptophan is described by Y = 0.94 X [plus or minus] 0.71 with a correlation coefficient of 0.86. Little, if any, tryptophan appears to reside in the ultrafiltrate fraction of the parotid fluid, whereas tyrosine peptides may be present. Only 40% of the Lowry positive material of the parotid fluid absorbed in the UV and appear to reside in the TCA precipitate fraction. Human parotid saliva contains approximately 2.5 mg% uric acid.