To ensure that only oocyte mRNA was analyzed in our study, oocyte RNA samples were examined for the ovarian form of aromatase, and all samples were deleted in which significant aromatase was detected. Thus, differences between our results and those in previous reports of activin subunit mRNA in oocytes using RT-PCR may be accounted for by residual granulosa cells adhering to oocytes at the time of extraction, since the oocytes were not individually examined before extraction and ovarian control PCR reactions were not performed. Furthermore, our failure to detect inhibin/activin subunit mRNA in oocytes is consistent with previous in situ hybridization studies.
On the other hand, the immunohistochemical detection of inhibin/activin subunit proteins in both oocytes and COC might represent activin and/or inhibin from granulosa cells bound to cell surface receptors on oocytes or internalized after receptor binding. Taken together, these results support the concept that granulosa cell-derived activin acts as a paracrine signal in developing oocytes. canadian health&care mall
Although ActRIIA and ActRIIB mRNAs have been previously demonstrated in mouse and rat oocytes, we provide evidence for the expression of these receptors in human oocytes, as well as detection of both ActRIA and ActRIB in mouse and human oocytes. Since type I and II receptors are both necessary for activin signal transduction, these findings provide support for the ability of oocytes to respond to activin during the maturation process.