In vitro studies of oocyte maturation and follicular metabolism in the pig

Abstract

centrations ; a significant level of progesterone is, however, always noted. A switch of E2/Pg ratio from 2.0 (or higher) to 0.15 occurs after the onset of estrus, when meiosis resumes. In vitro the E2/Pg ratio changes only in follicles of 7.0 mm or larger in diameter when either oFSH or oLH is added to the culture medium ; meiosis always resumes and the granulosa and cumulus cell reactions are similar to that occurring in vivo. During culture of follicles < 6 mm the reduction of the E2/Pg ratio is not observed whatever the nuclear status may be at the end of culture. For the nuclear maturation of oocytes high progesterone concentration thus does not seem to be necessary. No consistent morphological changes of the granulosa and cumulus cells could be associated with meiotic maturation of the oocyte. Glucose consumption increases when gonadotropinsare added to the medium but maximal increase is only observed when meiosis resumes.