Crespel A, De Boisvilliers F, Gros L, Kervran A
INSERM U-376, CHU Arnaud de Villeneuve, Montpellier, France.
Endocrinology. 1996 Sep;137(9):3674-80. doi: 10.1210/endo.137.9.8756532.
Glucagon is known to stimulate calcitonin secretion by thyroid C cells over a wide range of concentrations, raising the possibility of its interaction with several types of receptors. This study was designed to characterize receptors that mediate the effect of glucagon on a rat C cell line (CA-77). Binding studies, using radiolabeled [125I]glucagon and [125I]glucagon-like peptide-1-(7-36) amide ([125I]tGLP-1), to CA-77 plasma membranes demonstrated the presence of 1) a glucagon receptor with a dissociation constant (Kd) of 2.3 nM and relative potencies for structurally related peptides as follows: glucagon > oxyntomodulin > > tGLP-1; and 2) a tGLP-1 receptor with a Kd of 0.33 nM and relative potencies as follows: tGLP-1 > oxyntomodulin > glucagon. Glucagon stimulated calcitonin secretion from CA-77 cells in a dose-dependent manner over 4 orders of magnitude, with a maximal response of 312% over the basal value and an ED50 close to 50 nM. tGLP-1 induced a calcitonin release over 2 orders of magnitude, with a maximal response of 170% over the basal value and an ED50 close to 0.2 nM. Glucagon and tGLP-1 stimulated cAMP production in CA-77 cells to similar maximal levels over 4 and 2 orders of magnitude, respectively. The stimulation of cAMP production by glucagon at concentrations over 10 nM was suppressed by the tGLP-1 antagonist exendin-(9-39) amide, whereas the stimulation of calcitonin secretion was only partly abolished. Using a perifusion system of rat thyroid, glucagon and tGLP-1 stimulated calcitonin secretion in a calcium-dependent manner. It is concluded that glucagon and tGLP-1 receptors are expressed in the rat C cell line (CA-77) and in the normal rat thyroid. The effects of glucagon on calcitonin secretion observed at high concentrations are mediated in part through interaction with tGLP-1 receptors and via an additional non-cAMP-mediated mechanism.
已知胰高血糖素在很宽的浓度范围内可刺激甲状腺C细胞分泌降钙素，这增加了其与几种类型受体相互作用的可能性。本研究旨在鉴定介导胰高血糖素对大鼠C细胞系（CA - 77）作用的受体。使用放射性标记的[125I]胰高血糖素和[125I]胰高血糖素样肽-1-(7 - 36)酰胺（[125I]tGLP - 1）对CA - 77细胞膜进行结合研究，结果表明存在：1）一种胰高血糖素受体，其解离常数（Kd）为2.3 nM，对结构相关肽的相对效力如下：胰高血糖素＞胃泌酸调节素＞＞tGLP - 1；以及2）一种tGLP - 1受体，其Kd为0.33 nM，相对效力如下：tGLP - 1＞胃泌酸调节素＞胰高血糖素。胰高血糖素以剂量依赖方式刺激CA - 77细胞分泌降钙素，作用范围超过4个数量级，最大反应比基础值高312%，半数有效剂量（ED50）接近50 nM。tGLP - 1诱导降钙素释放的作用范围超过2个数量级，最大反应比基础值高170%，ED50接近0.2 nM。胰高血糖素和tGLP - 1分别在4个和2个数量级范围内刺激CA - 77细胞产生cAMP至相似的最大水平。tGLP - 1拮抗剂艾塞那肽-(9 - 39)酰胺可抑制浓度超过10 nM的胰高血糖素对cAMP产生的刺激作用，而对降钙素分泌的刺激作用仅部分被消除。使用大鼠甲状腺灌流系统，胰高血糖素和tGLP - 1以钙依赖方式刺激降钙素分泌。得出的结论是，胰高血糖素和tGLP - 1受体在大鼠C细胞系（CA - 77）和正常大鼠甲状腺中表达。高浓度时观察到的胰高血糖素对降钙素分泌的影响部分是通过与tGLP - 1受体相互作用以及通过一种额外的非cAMP介导机制介导的。
