Trimble E R, Bruzzone R, Biden T J, Meehan C J, Andreu D, Merrifield R B
Proc Natl Acad Sci U S A. 1987 May;84(10):3146-50. doi: 10.1073/pnas.84.10.3146.
In rat pancreatic acinar tissue adenylate cyclase is stimulated by low concentrations of secretin, while higher concentrations also activate phosphatidylinositol bisphosphate hydrolysis. By the use of the secretin analogues [Tyr10,13]secretin and [Tyr10,13,Phe22,Trp25]secretin, we have shown that substitution of tyrosine for leucine at positions 10 and 13 was sufficient to reduce the ability of the peptide to stimulate the production of inositol trisphosphate and the increases in cytosolic free calcium, while the ability to stimulate cAMP is little affected and the peptide remained a full agonist. Incubation with cholera toxin caused increases in cAMP, which were maximal after 30 min. Cholera toxin treatment also resulted in a marked reduction of secretin-stimulated inositol trisphosphate production, but this required a much more prolonged treatment (150-240 min), suggesting that different cholera toxin substrates were involved. Activation of protein kinase C with the phorbol ester phorbol 12-myristate 13-acetate had no effect on secretin-induced cAMP formation, nor was secretin-stimulated inositol trisphosphate formation altered by further increases in cAMP. These results indicate that the mechanisms by which secretin stimulates adenylate cyclase and activates phospholipase C in acinar tissue are completely independent.
在大鼠胰腺腺泡组织中，低浓度的促胰液素可刺激腺苷酸环化酶，而高浓度的促胰液素还可激活磷脂酰肌醇二磷酸水解。通过使用促胰液素类似物[酪氨酸10,13]促胰液素和[酪氨酸10,13,苯丙氨酸22,色氨酸25]促胰液素，我们发现，在第10位和第13位用酪氨酸取代亮氨酸足以降低该肽刺激肌醇三磷酸生成和胞质游离钙增加的能力，而刺激环磷酸腺苷（cAMP）的能力受影响较小，且该肽仍为完全激动剂。用霍乱毒素孵育可导致cAMP增加，30分钟后达到最大值。霍乱毒素处理还导致促胰液素刺激的肌醇三磷酸生成显著减少，但这需要更长时间的处理（150 - 240分钟），表明涉及不同的霍乱毒素底物。用佛波酯佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯激活蛋白激酶C对促胰液素诱导的cAMP形成没有影响，cAMP的进一步增加也不会改变促胰液素刺激的肌醇三磷酸形成。这些结果表明，促胰液素在腺泡组织中刺激腺苷酸环化酶和激活磷脂酶C的机制是完全独立的。
