MEASUREMENT OF FREE AND TOTAL HYDROXYPROLINE BY AUTOMATED FLOW-INJECTION OF SERUM OR URINE SAMPLES FROM MAINTENANCE HEMODIALYSIS-PATIENTS WITH RENAL OSTEODYSTROPHY

An automated measurement of total and free hydroxyproline in serum or urine is presented that uses flow injection analysis. After exclusion of nonspecific substances, hydroxyproline was oxidized by chloramine-T and L-cysteine with Ehrlich's reagent. The linearity obtained was fro m 3.8 mu mole/ L to 1.22 mmole/L with good precision (CV <3%). Compari son of the proposed method with HPLC yielded r=0.939 as the correlatio n coefficient. Reference intervals of free and total hydroxyproline ar e 1.4-9.7 mu mole/L, 3.8-27.2 mu mole/L for serum, and 10.0-72.5 mu mo le/L, 25.2-303.6 mu mole/L for urine, respectively. Serum free and tot al hydroxyproline levels in renal osteodystrophy patients on maintenan ce hemodialysis (N=71) were significantly higher than in controls (P<0 .0001). This method is superior to the use of HPLC with regard to stab ility of the color reaction. The measurement of serum free and total h ydroxyproline is a useful marker for therapeutic observation of renal osteodystrophy patients. (C) 1994 Wiley-Liss, Inc.