尽管kisspeptin在垂体中的重要性已经确立,kisspeptin的垂体作用的信号机制在很大程度上仍然未知。Somatolactin(SL),生长激素(GH)/催乳素(PRL)家族的成员,是一种在鱼类中具有多效性功能的垂体激素,但其由kisspeptin的调节尚未被检查。探讨kisspeptin在SL调节中的功能作用,在免疫鉴定的SLα细胞中证实了金鱼Kiss1受体的两个旁系同源物(Kiss1ra和Kiss1rb)的表达,而不是通过RT-PCR结合激光捕获显微切割分离的SLβ细胞。在从神经中间叶(NIL)制备的金鱼垂体细胞中,合成金鱼吻十肽(gKiss1-10和gKiss2-10)可以增加SLα的释放。与SLβ细胞中缺乏Kiss1r表达一致,SLβ的释放未被kisspeptin刺激改变。在平行实验中,金鱼gKiss1-10可以提高环磷酸腺苷(cAMP)的产量,上调蛋白激酶A(PKA)和蛋白激酶C(PKC)活性,并引发金鱼NIL细胞内Ca(2+)水平的快速升高。使用药理学方法,cAMP/PKA和磷脂酶C(PLC)/PKC途径以及随后的Ca(2)/钙调蛋白(CaM)依赖性级联激活被证明与gKiss1-10诱导的SLα释放有关。显然,Ca(2)依赖性级联反应是由细胞外Ca(2)通过电压敏感的Ca(2)通道进入和肌醇三磷酸敏感的细胞内Ca(2)存储的动员触发的。我们的结果表明,gKiss1-10可以通过受体后信号机制的复杂网络直接在垂体水平上触发SLα释放。
Although the importance of kisspeptin in the pituitary is firmly established, the signaling mechanisms for the pituitary actions of kisspeptin are still largely unknown. Somatolactin (SL), a member of the growth hormone (GH)/prolactin (PRL) family, is a pituitary hormone with pleiotropic functions in fish, but its regulation by kisspeptin has not been examined. To investigate the functional role of kisspeptin in SL regulation, expression of two paralogues of goldfish Kiss1 receptors (Kiss1ra and Kiss1rb) were confirmed in immunoidentified SLα but not SLβ cells isolated by RT-PCR coupled with laser capture microdissection. In goldfish pituitary cells prepared from neurointermediate lobe (NIL), synthetic goldfish Kiss decapeptides (gKiss1-10 and gKiss2-10) could increase SLα release. Consistent with the lack of Kiss1r expression in SLβ cells, SLβ release was not altered by kisspeptin stimulation. In parallel experiments, goldfish gKiss1-10 could elevate cyclic adenosine monophosphate (cAMP) production, upregulate protein kinase A (PKA) and protein kinase C (PKC) activities, and trigger a rapid rise in intracellular Ca(2+) levels in goldfish NIL cells. Using a pharmacological approach, cAMP/PKA and phospholipase C (PLC)/PKC pathways and subsequent activation of Ca(2+)/calmodulin (CaM)-dependent cascades were shown to be involved in SLα release induced by gKiss1-10. Apparently, the Ca(2+)-dependent cascades were triggered by extracellular Ca(2+) entry via voltage-sensitive Ca(2+) channels and mobilization of inositol trisphosphate-sensitive intracellular Ca(2+) stores. Our results demonstrate that gKiss1-10 can act directly at the pituitary level to trigger SLα release via a complex network of post-receptor signaling mechanisms.