TYROSINE CONFOUNDS OXIDATIVE ELECTROCHEMICAL DETECTION OF NITRIC-OXIDE

We report evidence that a a porphyrinic microsensor for detection of n itric oxide (NO) also detects biologically relevant concentration of t yrosine (Tyr) in dog brain. Tyr is oxidized by this sensor at the same potential as NO, and the sensitivity for NO an Tyr are of the same or der of magnitude. The interference from Tyr is of importance because 1 ) Tyr is abundant and 2) there is a concentration gradient of Tyr acro ss the blood-brain barrier that can lead to unpredictable results if d isturbed by ischemia or hypoxia. The knowledge of this interference is important for the interpretation of results obtained with this sensor and for the design of future studies.