Time courses of changes of para -, meta -, and ortho -tyrosine in septic patients: A pilot study.

Objectives: Sepsis is associated with oxidative stress. Due to oxidative stress, three tyrosine isoforms,para-,meta-, andortho-tyrosine (p-,m-, ando-Tyr), can be formed non-enzymatically in smaller amounts.p-Tyr is mainly formed physiologically in the kidneys through the activity of the phenylalanine hydroxylase enzyme. The three tyrosine isoforms may undergo different renal handling. Methods: Twenty septic patients were involved in the study and 25 healthy individuals served as controls. Blood and urine levels ofp-,m-, ando-Tyr were measured on admission and four consecutive days. Results: Serumm-Tyr levels were higher in septic patients than in controls on days 2 (P = 0.031) and 3 (P = 0.035). Serump-Tyr levels were lower in the cases than in controls on days 1 (P = 0.005) and 2 (P = 0.040), and subsequently normalized due to a day-by-day elevation (P = 0.002). The tendency of urinarym-Tyr concentration was decreasing (P = 0.041), while that of urinaryp-Tyr concentration was increasing (P = 0.001). Fractional excretion ofm-Tyr (FEm-Tyr) showed a decreasing tendency (P = 0.009), and was, on all days, higher than FEp-Tyr, which remained near-normal, less than 4%. Procalcitonin showed significant correlation with FEm-Tyr(r = 0.454;P < 0.001). Discussion: Our data suggest that the oxidative stress markerm-Tyr and physiologicp-Tyr may be handled differently in septic patients. The excretion ofm-Tyr correlates with inflammation.m-Tyr may be actively secreted or produced in the kidney in some patients, whereas the decreased serum level ofp-Tyr is a consequence of diminished renal production and not of renal loss. [ABSTRACT FROM AUTHOR]