Allaerts W, Tijssen A M, Jeucken P H, Drexhage H A, de Koning J
Department of Immunology, Erasmus University Rotterdam, The Netherlands.
Eur J Endocrinol. 1994 May;130(5):530-9. doi: 10.1530/eje.0.1300530.
Anterior pituitary cells cultured as three-dimensional cell aggregates and incubated with gonadotropin-releasing hormone (GnRH) show a biphasic pattern of luteinizing hormone (LH) release when steroid-free bovine follicle fluid is added to the culture medium. Initially, the GnRH-induced LH release is low (lag-phase response), but LH release increases during further incubations with GnRH (primed-state response). Also, in aggregates of dispersed cells from long-term ovariectomized rats cultured for 2 days in the presence of 1% bovine follicle fluid, a low initial LH responsiveness to GnRH could be restored. Cycloheximide was found to block the induction of the primed state, indicating the protein synthesis dependency of GnRH self-priming. In aggregates from gonadotroph-enriched cell populations obtained by velocity sedimentation in a bovine serum albumin gradient, addition of 1% bovine follicle fluid to the culture medium also restored a biphasic pattern of GnRH-induced LH release. However, co-culturing the gonadotroph-enriched cell aggregates with a folliculo-stellate (FS) cell-enriched population resulted in the attenuation of the differences in LH secretion rate between early and late responses to GnRH. The present example of the attenuation by folliculo-stellate cells of pituitary hormone secretion responses demonstrates that the cells regulate the cellular processes leading to a priming of the LH response to GnRH, rather than interfering with the access of GnRH to its receptor in gonadotrophs. Finally, it was found that stimulation of the adenylate cyclase enzyme with maximal effective doses of forskolin counteracted the inhibitory effect of bovine follicle fluid on the initial LH response to GnRH, but did not completely abolish the biphasic pattern of LH release. It is concluded that coupling to the adenylate cyclase enzyme is presumably involved in the LH surge inhibiting feedback action on the pituitary cells, but also other messenger pathways and intercellular interactions between pituitary cells may play a role in establishing a biphasic LH release at the pituitary level following GnRH administration.
当将无类固醇的牛卵泡液添加到培养基中时，培养为三维细胞聚集体并与促性腺激素释放激素（GnRH）一起孵育的垂体前叶细胞显示出促黄体生成素（LH）释放的双相模式。最初，GnRH诱导的LH释放较低（滞后阶段反应），但在与GnRH进一步孵育期间LH释放增加（预激发状态反应）。此外，在1%牛卵泡液存在下培养2天的长期卵巢切除大鼠的分散细胞聚集体中，对GnRH的低初始LH反应性可以恢复。发现放线菌酮可阻断预激发状态的诱导，表明GnRH自我预激发依赖蛋白质合成。在通过在牛血清白蛋白梯度中进行速度沉降获得的富含促性腺激素细胞群体的聚集体中，向培养基中添加1%牛卵泡液也恢复了GnRH诱导的LH释放的双相模式。然而，将富含促性腺激素细胞的聚集体与富含卵泡星状（FS）细胞的群体共培养导致对GnRH早期和晚期反应之间LH分泌率差异的减弱。卵泡星状细胞对垂体激素分泌反应的减弱的当前例子表明，这些细胞调节导致LH对GnRH反应预激发的细胞过程，而不是干扰GnRH与其在促性腺激素细胞中受体的结合。最后，发现用最大有效剂量的福斯可林刺激腺苷酸环化酶抵消了牛卵泡液对GnRH诱导的初始LH反应的抑制作用，但并未完全消除LH释放的双相模式。得出的结论是，与腺苷酸环化酶的偶联可能参与了LH峰对垂体细胞的抑制反馈作用，但其他信使途径以及垂体细胞之间的细胞间相互作用也可能在GnRH给药后在垂体水平建立双相LH释放中起作用。
