Variations in erythrocyte antioxidant XXXX peroxidase activity during the menstrual cycle.

@entity1 @entity1420 @entity16 @entity2041 @entity53 @entity2197 @entity134
OBJECTIVE: Antioxidant enzymes are an important part of the defence mechanisms against free @entity16 . Little is known, however, about the relationship between sex @entity134 hormones and cellular antioxidant systems. We have investigated the effect of physiological sex steroid changes on the erythrocyte antioxidant @entity2041 peroxidase ( @entity2197 -Px) activity during the menstrual cycle in a population of healthy normomenorrhoic @entity1 . DESIGN: Prospective, controlled. @entity1 : Ten normally cycling @entity1 (age range: 19-28 years; mean: 23.3 years) were recruited for alternate-day blood sampling from the first day of one menstrual bleed until the first day of the subsequent menstrual phase. MEASUREMENTS: Plasma was analysed for LH, FSH, @entity53 (E2) and @entity1420 (P4) concentrations. Erythrocyte @entity2197 -Px activity was evaluated on the same days in all subjects. Pyruvate-kinase (PK) activity, as an index of red blood cell population age, was also determined. RESULTS: All the @entity1 examined had a normal ovulatory cycle, as indicated by the hormone plasma pattern. Cycle length was standardized on the basis of the preovulatory E2 peak. Significant cycle phase-related changes in @entity2197 -Px (P < 0.03) were observed, with higher @entity2197 -Px activity levels being found from the later follicular to early luteal phase as compared to early follicular phase (chi 2 = 8.53, P < 0.001 and chi 2 = 5.54, P < 0.002, respectively). A significant positive correlation was observed between mean E2 and @entity2197 -Px cycle-related changes (r = 0.78, P = 0.001). Conversely, no significant cycle phase-dependent variations were detected in PK. CONCLUSIONS: The findings support the hypothesis that physiological ovarian E2 production during the menstrual cycle may play an important role in regulating erythrocyte @entity2041 peroxidase activity.
