Peroxidase activity in human granulocytes, inter- and intra-individual variations

A kinetic method for quantitation of peroxidase activity ('myeloperoxidase', E.C. 1.11.1.7.) in human granulocytes has been evaluated. The enzymic activity was determined at 37 degrees C, PH = 7.0. Substrates: 2-methyxo-phenol (1.25 mmol/l) and H2O2 (0.1 mmol/l). When applied on granulocytes from solitary blood samples from healthy, normal subjects the detected peroxidase activity varied considerably from one person to another (CV = 40-50%). Sequential determinations of the peroxidase activity in granulocytes from selected healthy, normal subjects demonstrated substantial intra-individual variations. Analysis of variance confirmed that the intra-individual variations (CV = 36%) exceeded all other variance components involved.