Hopkins C R, Walker A M
Mol Cell Endocrinol. 1978 Nov;12(2):189-208. doi: 10.1016/0303-7207(78)90114-4.
In cells dissociated from porcine anterior pituitary glands and maintained in culture for 48 h the specific secretagogue luteinizing hormone-releasing hormone (LH-RH) induces a biphasic pattern of luteinizing hormone (LH) release. A biphasic pattern of release is also induced by 57 X 10(-3) M K+ and the ionophore A-23187. By reducing the availability of Ca2+, either by omission from the medium, chelation or interfering with Ca2+ transport across the plasma membrane, it is shown that LH release stimulated by LH-RH is much less dependent upon the availability of extracellular Ca2+ than that stimulated by either high K+ or A-23187. Nevertheless, by using a lanthanum displacement protocol to follow the influx of 45Ca2+ it is shown that LH-RH stimulation does induce an influx of extracellular Ca2+. Parallel experiments in which the stimulated 45Ca2+ efflux from preloaded cells is followed confirm the influx data but suggest, in addition, that when the influx of extracellular Ca2+ is inhibited, the peptide is able to mobilize Ca2+ from an intracellular location. It is thus concluded that while LH release can be initiated by an increase in the intracellular level of Ca2+, and although LH-RH stimulation does increase the permeability of the plasma membrane to Ca2+, the stimulation of LH release by LH-RH is not dependent upon extracellular Ca2+.
在从猪脑垂体前叶分离并在培养中维持48小时的细胞中，特异性促分泌素促黄体生成激素释放激素（LH-RH）诱导促黄体生成激素（LH）释放呈现双相模式。57×10⁻³ M的K⁺和离子载体A-23187也能诱导释放的双相模式。通过从培养基中省略、螯合或干扰Ca²⁺跨质膜转运来降低Ca²⁺的可用性，结果表明，LH-RH刺激的LH释放比高K⁺或A-23187刺激的LH释放对细胞外Ca²⁺可用性的依赖性要小得多。然而，通过使用镧置换方案追踪⁴⁵Ca²⁺的流入，结果表明LH-RH刺激确实会诱导细胞外Ca²⁺的流入。在平行实验中，追踪预加载细胞中刺激后的⁴⁵Ca²⁺流出，证实了流入数据，但此外还表明，当细胞外Ca²⁺的流入受到抑制时，该肽能够从细胞内位置动员Ca²⁺。因此得出结论，虽然LH释放可以通过细胞内Ca²⁺水平的升高来启动，并且虽然LH-RH刺激确实会增加质膜对Ca²⁺的通透性，但LH-RH对LH释放的刺激并不依赖于细胞外Ca²⁺。
