Regulation and modulation of oocyte maturation in the bovine

Follicle enclosed oocytes are arrested at the prophase of the first meiotic division. Maturation of oocytes occurs in preovulatory follicles after the preovulatory LH surge concurrently with the final development of the preovulatory follicle. Although there is little doubt about the LH surge as the trigger for the resumption of meiosis, the intrafollicular signals that regulate the arrest before the LH peak and the resumption and progression of meiosis thereafter are still open to question. The available knowledge is predominantly obtained from in vitro maturation studies. This paper presents the state of the art on the action of endocrine and paracrine factors that affect the in vitro maturation of bovine oocytes either directly or mediated by cumulus cells. In particular, the effects of the gonadotropic hormones, growth hormone and several growth factors on nuclear and cytoplasmic maturation are discussed. (C) 1996 by Elsevier Science Inc.