Angiotensin-(1–7) in human follicular fluid correlates with oocyte maturation

Abstract STUDY QUESTION Do angiotensin (Ang)-(1–7) levels in human ovarian follicular fluid (FF) correlate with the number and proportion of mature oocytes obtained for IVF? SUMMARY ANSWER The present study shows for the first time that Ang-(1–7) levels in human FF correlate with the proportion of mature oocytes collected upon ovarian stimulation for IVF. WHAT IS KNOWN ALREADY Ang-(1–7) is an active peptide of the renin-angiotensin system that stimulates oocyte maturation in isolated rabbit and rat ovaries. However, its role in human ovulation remains unexplored. STUDY DESIGN, SIZE, DURATION This was a prospective cohort study including 64 participants from a single IVF center. Sample size was calculated to achieve a statistical power of 80% in detecting 20% differences in the proportion of mature oocytes between groups. The participants were enrolled in the study during six consecutive months. PARTICIPANTS/MATERIALS, SETTING, METHODS Plasma samples were obtained from all subjects at Day 21 of the last menstrual cycle before starting pituitary blockade and controlled ovarian stimulation (COS). Plasma and FF samples were quickly mixed with a protease inhibitor cocktail and stored at −80°C. Ang-(1–7) was quantified in plasma and FF samples by a highly sensitive and specific radioimmunoassay, which was preceded by solid phase extraction, speed vacuum concentration and sample reconstitution in assay buffer. FF Ang-(1–7) levels were stratified into tertiles and the patients of each tertile were compared for COS/IVF outcomes using Kruskal–Wallis ANOVA. Multiple regression analysis was used to adjust correlations for potential confounders. The mRNA encoding for Mas, a receptor for Ang-(1–7), was investigated by real-time PCR in luteinized granulosa cells purified from the FF. MAIN RESULTS AND THE ROLE OF CHANCE There was a four-fold increase in plasma Ang-(1–7) after ovulation induction (median 160.9 vs 41.4 pg/ml, P