Qian J M, Rowley W H, Jensen R T
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Am J Physiol. 1993 Apr;264(4 Pt 1):G718-27. doi: 10.1152/ajpgi.1993.264.4.G718.
Both gastrin and cholecystokinin (CCK) can stimulate pepsinogen release from chief cells, but controversy exists about the receptors or intracellular mediators involved. In the present study, we prepared isolated chief cells from guinea pig stomach (> 90% pure) to investigate the ability of gastrin and CCK to alter cell function. The COOH-terminal octapeptide of CCK (CCK-8) caused an eightfold increase in pepsinogen release (EC50, 54 nM). Both CCK-8 and gastrin increased inositol phosphates, with CCK-8 (1 microM) and gastrin (3 microM) causing a 40- and 14-fold increase in [3H]IP1, 10- and 6-fold for [3H]IP2, and 8- and 4-fold for [3H]IP3. CCK-8 caused a half-maximal increase in [3H]IP3 at 2 nM, and the dose-response curve was monophasic, whereas with gastrin the curve was biphasic, with an EC50 of the initial component (20% maximal) at 38 nM and the second component at 10 microM. L-364,718 (0.1 microM) inhibited the secondary increase seen with gastrin concentrations > 10 nM. The CCK-A-selective agonist A-71378 was 85-90% as efficacious as CCK-8 and was equally potent. With 0.1 microM L-364,718, A-71378 caused no increase in [3H]inositol phosphates until > 10 nM, whereas CCK-8 caused 15% of maximal increase at concentrations > 0.3 nM. Similar results were obtained with cytosolic calcium measured using fura-2 or on CCK-8- or gastrin-stimulated pepsinogen release. These results demonstrate that gastrin and CCK-8 can alter chief cell function by interacting with either a CCK-A or CCK-B/gastrin receptor. Both receptors are coupled to phospholipase C and cause changes in inositol phosphates, cytosolic calcium, and pepsinogen release; however, the intracellular amplification differs between the two receptor subtypes. Activation by CCK-related peptides of the CCK-A receptor subtype accounts for 85-90% of the maximal changes in cellular function, and activation of the CCK-B/gastrin receptor accounts for 10-20% of maximal changes.
胃泌素和胆囊收缩素（CCK）均可刺激主细胞释放胃蛋白酶原，但关于所涉及的受体或细胞内介质存在争议。在本研究中，我们从豚鼠胃中制备了分离的主细胞（纯度>90%），以研究胃泌素和CCK改变细胞功能的能力。CCK的羧基末端八肽（CCK-8）使胃蛋白酶原释放增加了8倍（半数有效浓度[EC50]为54 nM）。CCK-8和胃泌素均使肌醇磷酸增加，CCK-8（1 μM）和胃泌素（3 μM）分别使[3H]IP1增加40倍和14倍，[3H]IP2增加10倍和6倍，[3H]IP3增加8倍和4倍。CCK-8在2 nM时使[3H]IP3增加至最大值的一半，剂量-反应曲线为单相，而胃泌素的曲线为双相，初始成分（最大值的20%）的EC50为38 nM，第二成分的EC50为10 μM。L-364,718（0.1 μM）可抑制胃泌素浓度>10 nM时出现的继发性增加。CCK-A选择性激动剂A-71378的效力为CCK-8的85-90%，且效力相当。使用0.1 μM L-364,718时，A-71378在浓度>10 nM时才会使[3H]肌醇磷酸增加，而CCK-8在浓度>0.3 nM时可使增加至最大值的15%。使用fura-2测量胞质钙或检测CCK-8或胃泌素刺激的胃蛋白酶原释放时，也得到了类似的结果。这些结果表明，胃泌素和CCK-8可通过与CCK-A或CCK-B/胃泌素受体相互作用来改变主细胞功能。两种受体均与磷脂酶C偶联，导致肌醇磷酸、胞质钙和胃蛋白酶原释放发生变化；然而，两种受体亚型的细胞内放大作用有所不同。CCK相关肽激活CCK-A受体亚型可导致细胞功能最大变化的85-90%，激活CCK-B/胃泌素受体可导致最大变化的10-20%。
