title: Intra-ovarian roles of activins and inhibins.
abstract: Granulosa cells are the main ovarian source of inhibins, activins and activin-binding protein (follistatin) while germ (oogonia, oocytes) and somatic (theca, granulosa, luteal) cells express activin receptors, signaling components and inhibin co-receptor (betaglycan). Activins are implicated in various intra-ovarian roles including germ cell survival and primordial follicle assembly; follicle growth from preantral to mid-antral stages; suppression of thecal androgen production; promotion of granulosa cell proliferation, FSHR and CYP19A1 expression; enhancement of oocyte developmental competence; retardation of follicle luteinization and/or atresia and involvement in luteolysis. Inhibins (primarily inhibin A) are produced in greatest amounts by preovulatory follicles (and corpus luteum in primates) and suppress FSH secretion through endocrine negative feedback. Together with follistatin, inhibins act locally to oppose auto-/paracrine activin (and BMP) signaling thus modulating many of the above processes. The balance between activin-inhibin shifts during follicle development with activin signalling prevailing at earlier stages but declining as inhibin and betaglycan expression rise.
authors.affiliation: School of Biological Sciences, Hopkins Building, University of Reading, Whiteknights, Reading RG6 6UB, UK. p.g.knight@reading.ac.uk
authors.forename: Phil G
authors.initials: PG
authors.lastname: Knight
authors.forename: Leanne
authors.initials: L
authors.lastname: Satchell
authors.forename: Claire
authors.initials: C
authors.lastname: Glister
mesh_terms: D029404:Activin Receptors / Q000378:metabolism; D028341:Activins / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D030762:Estrous Cycle / Q000378:metabolism; D005260:Female; D006801:Humans; D007265:Inhibins / Q000378:metabolism / Q000502:physiology*; D008597:Menstrual Cycle / Q000378:metabolism; D006080:Ovarian Follicle / Q000378:metabolism* / Q000502:physiology; D010053:Ovary / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction
chemical_list: D028341:Activins; D007265:Inhibins; D029404:Activin Receptors