Gespach C, Bataille D, Vauclin N, Rosselin G, Moroder L, Wünsch E
Peptides. 1981;2 Suppl 2:247-51. doi: 10.1016/0196-9781(81)90039-5.
Specific binding sites for secretin have been identified in rat fundic membranes, using 125I-secretin. The binding was saturable, reversible, time and temperature dependent. Optimal pH for binding was around 7-7.5. Scatchard plots were compatible with the existence of 2 classes of receptors; the first class with a high affinity for secretin (apparent Kd of 4 x 10(-10) M) and a low binding capacity (150 fmol per mg membrane protein, i.e., 4,500 high affinity sites/cell) and a class of receptors with a lower affinity (Kd of 3 x 10(-9) M) and a higher binding capacity (580 fmol per mg membrane protein i.e., 17,400 sites/cell). Glucagon, gastric inhibitory polypeptide and somatostatin had no-effect on secretin binding. In contrast, VIP inhibited 125I-secretin binding and stimulated adenylate cyclase activity, in both cases at a 200-times lower potency than secretin (ID50 and Ka = 2 x 10(-7) M VIP). The properties of these secretin receptors strongly support the concept that secretin acts as a regulatory peptide on the rat gastric epithelium.
利用125I-促胰液素，在大鼠胃底膜中已鉴定出促胰液素的特异性结合位点。该结合具有饱和性、可逆性，且依赖时间和温度。结合的最佳pH约为7 - 7.5。Scatchard图与两类受体的存在相符；第一类对促胰液素具有高亲和力（表观解离常数Kd为4×10(-10) M）且结合能力低（每毫克膜蛋白150 fmol，即每个细胞有4500个高亲和力位点），另一类受体亲和力较低（Kd为3×10(-9) M）且结合能力较高（每毫克膜蛋白580 fmol，即每个细胞有17400个位点）。胰高血糖素、胃抑制性多肽和生长抑素对促胰液素结合无影响。相反，血管活性肠肽抑制125I-促胰液素结合并刺激腺苷酸环化酶活性，在这两种情况下其效力均比促胰液素低200倍（血管活性肠肽ID50和Ka = 2×10(-7) M）。这些促胰液素受体的特性有力地支持了促胰液素作为大鼠胃上皮调节肽发挥作用的概念。
