FSH ISOFORMS - BIO AND IMMUNO-ACTIVITIES IN POSTMENOPAUSAL AND NORMALMENSTRUATING WOMEN

OBJECTIVE The full expression of gonadotrophin biological activity dep ends on the gonadotrophin carbohydrate component. Our aim was to study serum FSH isoforms present in the follicular phase (FPS) and in the m enopause (PMS) since the endocrine status may influence the structure of incorporated oligosaccharides. SUBJECTS Ten healthy post-menopausal women (age range 53-68) not receiving any hormonal treatment and 10 h ealthy women (age range 20-28) in the follicular phase of their menstr ual cycle were studied. MEASUREMENTS Bio and immune FSH-activities (Se rtoli cell aromatase induction assay and RIA, respectively) were deter mined in separated isoforms after concanavalin A chromatography. Isola ted isoforms were: UB, unbound; WE, weakly bound and FB, firmly bound to the lectin. RESULTS PMS showed two groups of immune and bioactive F SH isoforms: WE, bearing biantennary galactosylated type and FB, beari ng high mannose or hybrid type oligosaccharides. Immune and bio-active FSH were not detected in the UB fractions. WE isoforms represented 82 +/-6% of the total bioactivity recovered in samples analysed individua lly; their B/l ratio was 0.85+/-0.20. FB isoforms were 18+/-6%; their B/l ratio was 3.27+/-0.60. Whole serum B/l ratio was 1.20+/-0.30. Simi lar results were obtained when pooled sera was analysed: WE: 77%, B/l: 0.82; WB: 23%, B/l: 3.75, Whole serum B/l in pooled samples was 1.10. FPS showed a different pattern. Us isoforms, bearing triantennary or bisecting oligosaccharides, were 41+/-3% of the total bioactivity reco vered in samples analysed individually. Their B/l ratio was 0.61+/-0.2 3. WE isoforms were 59+/-13% and their B/l 0.76+/-0.14. FB FSH isoform s were not detected. The whole serum B/l ratio was 0.60+/-0.30. Simila r results were obtained when pooled sera was analysed: WE 43%, B/l 0.4 2; FB 57%, B/l 0.62. Whole serum B/l in pooled samples was 0.70. CONCL USIONS These results show that, in normal women, circulating FSH bioac tivity is associated with isoforms with different oligosacharide struc tures according to hormonal status. FSH in the follicular phase has a higher degree of branching and a more complete carbohydrate chain than the FSH secreted during the menopause.