Induction and inhibition of in vitro oocyte maturation and production of steroids in fish follicles by forskolin

Publisher Website
Google Scholar
Abstract
The effects of forskolin (FK) on in vitro oocyte maturation and production of steroids were examined in Oryzias latipes. When oocytes within preovulatory follicles were preincubated in the presence of FK for 2–10 hr, they matured normally after additional incubation for 10–20 hr in plain culture medium. Naked (follicle cell‐free) oocytes did not mature under these conditions. FK stimulated dose‐dependent production of steroids (estradiol‐17β, E2, and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one, 17α,20β‐diOHprog) and cAMP in follicle (granulosa) cells. On the other hand, exposure to FK within 2 hr after 17α,20β‐diOH prog stimulation caused reversible inhibition of gonadotropin (PMS)‐ or 17α,20β‐diOH prog‐induced maturation of the intrafollicular oocytes in vitro. FK also significantly inhibited the 17α,20β‐diOHprog‐induced maturation of naked oocytes, suggesting the existence of adenylate cyclase in fish oocytes. These data indicate that in Oryzias latipes, FK induces oocyte maturation by stimulating follicular production of maturation‐inducing steroid (MIS), probably 17α,20β‐diOH prog, via an increase in cAMP, and that it may inhibit oocyte maturation by increasing ooplasmic cAMP and some inhibitory interaction between the granulosa cells and the oocyte through intercellular communication.