Foxcroft G R, Hunter M G, Grant S A
AFRC Research Group on Hormones and Farm Animal Reproduction, University of Nottingham, Faculty of Agricultural Science, Sutton Bonington, Loubhborough, U.K.
Acta Physiol Pol. 1989 Jan-Feb;40(1):53-63.
Exogenous gonadotrophin (eg. PMSG) treatment results in follicular growth in most reproductive states, and suggests that lack of FSH and LH-like activity is a likely cause of arrested-follicular development in the pig. Endogenous changes in gonadotrophins between reproductive and non-reproductive states are consistent with this concept. However, changes in the pattern of LH secretion, rather than clearly defined changes in FSH release, appear to be the effective trigger for follicular recruitment. In other situations in vivo, follicular growth is initiated in the absence of demonstrable changes in LH or FSH secretion, suggesting that other hormones interact to sensitize the ovary to gonadotrophins. Such effects have been reported for insulin, cortisol, thyroxine and IGF-1 in vitro, and the steroid environment of follicles also affects gonadotrophin receptors and receptor-mediated mechanisms. Once initiated, the regulation of follicle maturation also involves interactions between gonadotrophins and steroids, as well as other intra-ovarian regulators. Co-operation exists between theca and granulosa in the synthesis of steroids and androgen precursor availability is an important regulator of the oestrogenic activity of follicles. Considerable heterogeneity exists in the morphological and biochemical maturity of preovulatory follicles and inter-follicular regulation via endocrine and paracrine mechanisms may be an essential component of the selection process.
外源性促性腺激素（如孕马血清促性腺激素）治疗在大多数生殖状态下都会导致卵泡生长，这表明缺乏促卵泡素（FSH）和促黄体生成素（LH）样活性可能是猪卵泡发育停滞的原因。生殖状态和非生殖状态之间促性腺激素的内源性变化与这一概念相符。然而，促黄体生成素分泌模式的变化，而非促卵泡素释放的明确变化，似乎是卵泡募集的有效触发因素。在体内的其他情况下，卵泡生长在促黄体生成素或促卵泡素分泌无明显变化时就已启动，这表明其他激素相互作用使卵巢对促性腺激素敏感。体外实验已报道胰岛素、皮质醇、甲状腺素和胰岛素样生长因子-1（IGF-1）有此类作用，卵泡的类固醇环境也会影响促性腺激素受体及受体介导机制。一旦启动，卵泡成熟的调节还涉及促性腺激素与类固醇之间的相互作用，以及其他卵巢内调节因子。卵泡膜细胞和颗粒细胞在类固醇合成过程中存在协同作用，雄激素前体的可利用性是卵泡雌激素活性的重要调节因子。排卵前卵泡在形态和生化成熟度上存在相当大的异质性，通过内分泌和旁分泌机制进行的卵泡间调节可能是选择过程的重要组成部分。
