Measurement of Vaginal Myeloperoxidase Activity

Myeloperoxidase activity (MPO), an index of polymorphonuclear cell accumulation, was determined in the vaginal tissues, as previously described [26 (link)]. Vaginal tissues collected at the specified time were homogenized in a solution containing 0.5% hexa-decyl-trimethyl-ammonium bromide dissolved in 10 mm potassium phosphate buffer (pH 7) and centrifuged for 30 min at 20,000× g at 4 °C. An aliquot of the supernatant was then allowed to react with a solution of tetra-methyl-benzidine (1.6 mm) and 0.1 mm H₂O₂. The rate of change in absorbance was measured spectrophotometrically at 650 nm using a Thermo Scientific™ Multiskan FC Microplate Spectrophotometer (Model: 51119100). MPO activity was expressed in units/mg protein.