AOPP Determination
AOPP concentration was assessed in plasma according to the
spectrophotometric method of Witko-Sarsat et al18 and expressed
in equivalents of chloramine T. The absolute concentration
of AOPP is dependent on both individual protein
concentration and the efficacy of oxidative modification. Because
albumin, the main substrate for AOPP formation in
plasma,6 is significantly depleted in IBD,19 we determined
relative AOPP concentration instead of absolute AOPP concentration.
Determination of relative AOPP allows for evaluation
of whether the proportion of oxidatively modified
proteins (the ratio of AOPPs to protein content) is altered.
Relative AOPP (rAOPP), defined as the absolute AOPP concentration
divided by the corresponding albumin level, was
expressed in micromoles of absolute AOPP per gram of
albumin (mol/g). Albumin level was determined with the
bromocresol green method based on the colorimetric assessment
of albumin– dye complex with reagents supplied by
Stamar (Dabrowa Gornicza, Poland).