VARIATIONS IN ERYTHROCYTE ANTIOXIDANT GLUTATHIONE-PEROXIDASE ACTIVITYDURING THE MENSTRUAL-CYCLE

OBJECTIVE Antioxidant enzymes are an important part of the defence mec hanisms against free radical damage. Little is known, however, about t he relationship between sex steroid hormones and cellular antioxidant systems, We have investigated the effect of physiological sex steroid changes on the erythrocyte antioxidant glutathione peroxidase (GSH-Px) activity during the menstrual cycle in a population of healthy normom enorrhoic women, DESIGN Prospective, controlled, PATIENTS Ten normally cycling women (age range: 19-28 years; mean: 23.3 years) were recruit ed for alternate-day blood sampling from the first day of one menstrua l bleed until the first day of the subsequent menstrual phase. MEASURE MENTS Plasma was analysed for LH, FSH, oestradiol (E2) and progesteron e (P-4) concentrations, Erythrocyte GSH-Px activity was evaluated on t he same days in all subjects, Pyruvate-kinase (PK) activity, as an ind ex of red blood cell population age, was also determined, RESULTS All the women examined had a normal ovulatory cycle, as indicated by the h ormone plasma pattern, Cycle length was standardized on the basis of t he preovulatory E-2 peak. Significant cycle phase-related changes in G SH-Px (P< 0.03) were observed, with higher GSH-Px activity levels bein g 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 E-2 and GSH-Px cycle-related changes (r= 0.78, P= 0 001) . Conversely,no significant cycle phase-dependent variations were dete cted in PK, CONCLUSIONS The findings support the hypothesis that physi ological ovarian E-2 production during the menstrual cycle may play an important role in regulating erythrocyte glutathione peroxidase activ ity.