Mammalian folliculogenesis involves the developmental progression from primordial follicles, containing a single layer of granulosa cells surrounding an oocyte, to large preovulatory follicles consisting of multiple layers of mural granulosa cells enclosing a cumulus-oocyte complex. During this process, the enclosed oocyte undergoes cytoplasmic, then nuclear maturation, resulting in a fully competent oocyte arrested at the second meiotic metaphase by the time of ovulation. The entire process is regulated and coordinated by endocrine hormones such as the gonadotropins, and by local factors that allow communication between somatic cells as well as between somatic cells and oocytes. In many cases, however, the molecular nature of these signals is only now being elucidated. canadian family pharmacy
Inhibins and activins are members of the transforming growth factor p (TGFp) superfamily of growth and differentiation factors. Inhibins are heterodimers containing distantly related a and p (pA or pB) subunits, while activins are p-subunit homodimers. Follistatin (FS) is a structurally unrelated monomeric protein with several alternatively spliced molecular forms (designated FS288 and FS315) that irreversibly bind activin and neutralize activin’s biological effects.