Berkowitz J M, Praissman M, LeFevre M E
Am J Physiol. 1976 Aug;231(2):573-8. doi: 10.1152/ajplegacy.1976.231.2.573.
The actions of human synthetic gastrin I(G), the C-terminal tetrapeptide of gastrin (T), and the C-terminal octapeptide of cholecystokinin (OP) on acid secretion and transepithelial potential difference (PD) of the isolated Necturus gastric mucosa were determined. All three peptides induced H+ secretion, but the maximum H+ output was less with OP than with G or T. G and OP produced their maximum H+ output at lower molar concentrations than T. G- and OP-stimulated secretion was long sustained, but T-stimulated secretion rapidly returned to basal levels. T- and G-stimulated secretion was partially inhibited by the addition of OP. Evidence is presented that T rapidly disappears from solutions exposed to gastric mucosa, whereas G does not. Washing sensitized the mucosa to subsequent addition of T. The results suggest that the action of the common C-terminal tetrapeptide of G, T, and OP is modified by the preceding amino acid sequences, and that T, the smallest of the three peptides, is rapidly degraded by gastric tissue in vitro. The implications of the work for the study of gastrointestinal hormone structure-function relationships in isolated tissue preparations are discussed.
测定了人合成胃泌素I（G）、胃泌素C末端四肽（T）和胆囊收缩素C末端八肽（OP）对离体美西螈胃黏膜酸分泌和跨上皮电位差（PD）的作用。所有这三种肽均诱导H⁺分泌，但OP诱导的最大H⁺分泌量低于G或T。G和OP在比T更低的摩尔浓度下产生最大H⁺分泌量。G和OP刺激的分泌持续时间长，但T刺激的分泌迅速恢复到基础水平。添加OP可部分抑制T和G刺激的分泌。有证据表明，T在暴露于胃黏膜的溶液中迅速消失，而G则不会。冲洗使黏膜对随后添加的T敏感。结果表明，G、T和OP共同的C末端四肽的作用受到前面氨基酸序列的影响，并且三种肽中最小的T在体外被胃组织迅速降解。讨论了这项工作对离体组织制剂中胃肠激素结构 - 功能关系研究的意义。
