Bovine oocyte and embryo development following meiotic inhibition with butyrolactone I

In this study we have shown that butyrolactone I (BL-I), a potent inhibitor of cyclin-dependent kinases, inhibits meiotic resumption in bovine oocytes by blocking germinal vesicle breakdown in a dose-dependent manner. A conce ntration 100 mu M blocked over 60% of oocytes, while 150 mu M inhibited alm ost all oocytes compared to the control in which over 80% resumed meiosis. Following a second 24 hr culture under conditions permissive to normal matu ration, almost all (95%) of blocked oocytes resumed meiosis and progressed to metaphase II. In terms of developmental competence, oocytes maintained i n meiotic arrest for 24 hr with 100 mu M exhibited a similar capacity to de velop to the blastocyst stage as nonblocked control oocytes following matur ation, fertilization, and culture in vitro. Cryopreservation was employed a s a tool to detect differences in the oocyte viability between blocked and control oocytes. Cleavage of oocytes was significantly reduced following vi trification and activation both in BL-I treated (40.2% vs. 71.9%, P < 0.05) and the control groups (45.6% vs. 81.7%, P < 0.05). However, BL-I treated oocytes were less likely to develop into blastocysts following vitrificatio n (20.0% from vitrified vs 42.5% from nonvitrified cleaved oocytes, P < 0.0 5, based on cleaved oocytes) compared to nontreated oocytes (34.0% from vit rified vs. 42.9% from nonvitrified oocytes, P < 0.05). These results demons trate the feasibility of maintaining bovine oocytes in artificial meiotic a rrest without compromising their subsequent developmental competence and ma y represent a tool for improving the development of less competent oocytes. Mol. Reprod. Dev. 57:204-209, 2000. (C) 2000 Wiley-Liss, Inc.