A fluorometric method for the estimation of tyrosine in plasma and tissues.

Abstract

The reaction between 1-nitroso-2-naphthol and tyrosine, under suitable conditions, yields a yellow product which has been utilized for the colorimetric estimation of tyrosine in biologic material. It has now been found that the nitrosonaphthol derivative of tyrosine fluoresces. Measurement of the fluorescence of this derivative endows the procedure of Undenfriend and Cooper with greater sensitivity and specificity than was obtained in their original colorimetric method. In this report, the fluorometric method is used to determine the amount of tyrosine in plasma from fasting patients with different disease states, as compared to the amount of the amino acid found in the plasma of normal fasting controls. A few of the patients selected had diseases in which it was thought that an alteration in tyrosine metabolism might occur. The survey is not intended as a critical analysis of tyrosine plasma levels, but rather to demonstrate the method and its application.