Effect of sialylation and complexity of FSH oligosaccharides on inhibin production by granulosa cells

Granulosa cell inhibin A and B production is regulated by FSH and gonadal factors. This gonadotrophin is released as a mixture of glycoforms, which induce different biological responses in vivo and in vitro. Our aim was to determine the effect of recombinant human FSH glycosylation variants on inhibin A and B production by rat granulosa cells. Preparative isoelectrofocusing was used to isolate more acidic/sialylated (pH5.00) rhFSH charge analogues. Concanavalin-A was used to isolate unbound and firmly bound rhFSH glycoforms on the basis of their oligosaccharide complexity. Granulosa cells, obtained from oestrogen-primed immature rats, were cultured with either native rhFSH or its glycosylation variants. Inhibin A and B were determined using specific ELISAs. Results were expressed as mean±SEM. Under basal conditions inhibin A was the predominant dimer produced (inhibin A: 673±55; inhibin B: 80±4 pg/mL). More acidic/sialylated charge analogues stimulated inhibin B production when compared to inhibin A at all doses studied; in contrast, less acidic/sialylated charge analogues stimulated inhibin A production and elicited no effect on inhibin B. Glycoforms bearing complex oligosaccharides showed a potent stimulatory effect on inhibin B when compared to inhibin A production (i.e. dose 1ng/mL: 4.9±0.5vs0.9±0.1 fold stimulation, P