Fitzpatrick L A, Chin H, Nirenberg M, Aurbach G D
Metabolic Diseases Branch, National Institutes of Health, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1988 Apr;85(7):2115-9. doi: 10.1073/pnas.85.7.2115.
We have shown previously that Ca2+-channel agonists, which open Ca2+ channels, inhibit parathyroid hormone (PTH) secretion from dispersed bovine parathyroid cells, whereas Ca2+-channel antagonists, which close Ca2+ channels, stimulate PTH release. We now have tested the effects of mouse antibodies specific for purified alpha subunits of rat skeletal muscle Ca2+-channel proteins on PTH secretion by bovine parathyroid cells in vitro. Mouse antisera (MC-2, MC-3, MC-4) blocked the secretion of PTH from parathyroid cells incubated with 0.5 mM Ca2+ ions. Affinity-purified MC-4 antibodies inhibited PTH release in a concentration-dependent manner. Incubation of parathyroid cells with pertussis toxin markedly reduced MC-4-dependent inhibition of PTH secretion. Parathyroid cell membrane proteins were fractionated by NaDodSO4/polyacrylamide gel electrophoresis under either reducing or nonreducing conditions and immunoblotted with MC-4 antiserum. Antibodies bound to one major band of protein with Mr approximately equal to 150,000. These results suggest that the antibodies bind to Ca2+-channel alpha subunits and act as agonists that open the channels and inhibit PTH release.
我们之前已经表明，打开钙离子通道的钙离子通道激动剂可抑制分散的牛甲状旁腺细胞分泌甲状旁腺激素（PTH），而关闭钙离子通道的钙离子通道拮抗剂则刺激PTH释放。我们现在测试了针对大鼠骨骼肌钙离子通道蛋白纯化α亚基的小鼠抗体对体外培养的牛甲状旁腺细胞分泌PTH的影响。小鼠抗血清（MC - 2、MC - 3、MC - 4）可阻断与0.5 mM钙离子一起孵育的甲状旁腺细胞分泌PTH。亲和纯化的MC - 4抗体以浓度依赖的方式抑制PTH释放。用百日咳毒素孵育甲状旁腺细胞可显著降低MC - 4对PTH分泌的抑制作用。在还原或非还原条件下，通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳对甲状旁腺细胞膜蛋白进行分级分离，并用MC - 4抗血清进行免疫印迹。抗体与一条主要的蛋白带结合，其分子量约为150,000。这些结果表明，抗体与钙离子通道α亚基结合，并作为打开通道并抑制PTH释放的激动剂起作用。
