Wood C A, Schofield J G
Department of Biochemistry, School of Medical Sciences, University of Bristol, U.K.
Biochim Biophys Acta. 1989 Sep 4;1013(1):97-106. doi: 10.1016/0167-4889(89)90134-1.
Addition of thyrotropin-releasing hormone (TRH) (10 nM to 10 microM) to bovine anterior pituitary cells labelled with [3H]inositol decreased the radioactivity in inositol-containing lipids and increased it in inositol phosphates. TRH also increased the cytoplasmic calcium concentration biphasically. At TRH concentrations below 10 nM, the increase was sustained and sensitive to inhibitors of calcium influx through voltage-gated channels, whereas concentrations over 10 nM elicited in addition a rapid transient increase in calcium, which was relatively insensitive to such inhibition. Incubation of the cells in medium containing 25 mM KCl increased the cytoplasmic calcium concentration by stimulating influx through voltage-gated channels, and markedly enhanced the initial transient increase of calcium seen at TRH concentrations above 10 nM. It did not affect the generation of InsP3 and it also enhanced the calcium response to ionomycin. It is suggested that stimulation of calcium entry through voltage-gated channels can increase the amount of calcium available for mobilisation by TRH.
向用[3H]肌醇标记的牛垂体前叶细胞中添加促甲状腺激素释放激素（TRH）（10 nM至10 microM），会降低含肌醇脂质中的放射性，并增加肌醇磷酸中的放射性。TRH还双相增加细胞质钙浓度。在TRH浓度低于10 nM时，增加是持续的，并且对通过电压门控通道的钙内流抑制剂敏感，而浓度超过10 nM时，还会引起钙的快速瞬时增加，这种增加对这种抑制相对不敏感。将细胞在含有25 mM KCl的培养基中孵育，通过刺激电压门控通道内流来增加细胞质钙浓度，并显著增强在TRH浓度高于10 nM时看到的钙的初始瞬时增加。它不影响肌醇三磷酸（InsP3）的生成，并且还增强了对离子霉素的钙反应。提示通过电压门控通道刺激钙内流可增加TRH动员的可利用钙量。
