Fertilization and early development of rat oocytes induced to mature by forskolin

Forskolin has been shown to successfully induce maturation of rat oocytes as assessed by morphological markers. The present study was designed in an attempt to elucidate whether oocytes, induced to mature by forskolin (10^-4 M, group A) in a follicle-enclosed oocyte culture, are fertilizable and can further develop into two-cell embryos. Oocytes exposed in vitro to either luteinizing hormone (LH, 5 μg/ml, group B) or a GnRH agonist analogue (10^-7 M, group C) as well as oocytes that underwent maturation in vivo (group D), served as positive controls. We found that similar rates of fertilization were obtained in the experimental and all of the above mentioned control groups (A = 78.9 ± 4.2%, B = 77.9 ± 3.1%, C = 77.5 ± 5.5% and D = 84.7 ± 2.7%). Cleavage rate of fertilized eggs from group A was significantly higher than that of eggs from groups B & C, and similar to that of eggs from group D A = 63.1 ± 6.7%, B = 37.8 ± 4.9%, C = 50.0 ± 4.1%, D = 67.8 ± 4.1%). Using functional parameters we hereby demonstrate that forskolin and LH are at least equally potent in producing fertilizable eggs that have a high potential of development into two cell embryos. These results further support the idea that cAMP is a mediator of LH action in inducing oocyte maturation.