In addition, in vitro studies have indicated a role for activin in promoting meiotic and cytoplasmic maturation of the oocyte as well as influencing the outcome of in vitro maturation and fertilization of bovine oocytes. Taken together, these studies suggest that oocytes respond to activin in at least two ways: 1) by producing one or more factors that regulate the organization and maturation of developing follicles and 2) by modulating its own maturation. However, it is presently unknown whether oocytes produce activin directly or respond in a paracrine fashion to granulosa-derived activin under in vivo conditions. buy cipro
To determine whether oocytes can produce inhibin, ac-tivin, or FS and whether they possess type I receptors necessary for responding to activin, we examined mRNA expression of inhibin/activin subunits, FS, and the type I and II activin receptor subtypes in oocytes. These results were compared to the mRNA expression pattern in cumulus granulosa cells. To accomplish this largely single-cell analytical procedure, a highly sensitive and specific reverse transcription-polymerase chain reaction (RT-PCR) protocol was developed. Our results indicate that neither human nor mouse oocytes contain detectable levels of activin subunit mRNA but that they express a full complement of activin receptor subtype mRNAs, consistent with the capability of responding to, but not synthesizing, activin.