U73122 inhibits Ca2+ oscillations in response to cholecystokinin and carbachol but not to JMV-180 in rat pancreatic acinar cells.
U73122 inhibits Ca2+ oscillations in response to cholecystokinin and carbachol but not to JMV-180 in rat pancreatic acinar cells.
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DOI：
10.1016/s0021-9258(19)49643-9
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发表时间：
1992-07
期刊：
影响因子：
--
通讯作者：
D. Yule;J. Williams
中科院分区：
文献类型：
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作者：
D. Yule;J. Williams
用低浓度的磷脂酰肌醇（PI）连接的促分泌素刺激大鼠胰腺腺泡细胞诱导[Ca 2 +]i振荡，而在肌醇1，4，5-三磷酸的形成中没有可测量的变化。因此，我们测试了一种新的磷脂酶C抑制剂U 73122，以确定PI周转是否是产生[Ca 2 +]i振荡所必需的。在腺泡预标记的[3 H]肌醇，PI水解刺激胆囊收缩素或卡巴胆碱被抑制剂量依赖性的U 73122，在10 μ M的最大效果;肌醇1，4，5-三磷酸的形成，使用放射受体测定法测量，也同样受到抑制。相比之下，促胰液素或血管活性肠肽刺激产生的cAMP不受10 μ M U 73122的影响。这些研究表明，U 73122是一个相对特异性的G-蛋白介导的磷脂酶C激活胰腺腺泡抑制剂。在fura-2负载腺泡中，U 73122抑制了这些高浓度促分泌素刺激的[Ca 2 +]i的增加，这可以证明引起PI周转。用氟化钠直接刺激G蛋白产生的[Ca ~（2+）]i信号也被U 73122抑制;然而，毒胡萝卜素诱导的[Ca ~（2+）]i升高不受影响。这些数据表明，抑制的机制是远端的细胞表面受体的占领，但不涉及一般的钙代谢的干扰。当低浓度胆囊收缩素或卡巴胆碱引起[Ca ~（2+）]i振荡时，U 73122迅速抑制振荡[Ca ~（2+）]i信号。与此相反，胆囊收缩素，JMV-180，它不刺激PI代谢的变化在任何浓度的类似物诱导的振荡，不受影响。这表明胆囊收缩素和卡巴胆碱诱导的振荡可能是由PI代谢的小的局部变化引起的，这是不容易检测到的。然而，U 73122不能抑制JMV-180诱导的振荡表明PI代谢可能不一定是产生[Ca 2 +]i振荡的先决条件。
Stimulation of rat pancreatic acinar cells with low concentrations of phosphatidylinositol (PI)-linked secretagogues induces [Ca2+]i oscillations, without measurable changes in the formation of inositol 1,4,5-trisphosphate. Therefore, we tested U73122 a new phospholipase C inhibitor to determine if PI turnover is necessary for the generation of [Ca2+]i oscillations. In acini prelabeled with [3H]inositol, PI hydrolysis on stimulation with either cholecystokinin or carbachol was inhibited dose-dependently by U73122, with a maximal effect seen at 10 microM; the formation of inositol 1,4,5-trisphosphate, measured using a radioreceptor assay, was also similarly inhibited. By contrast secretin- or vasoactive intestinal peptide-stimulated production of cAMP was unaffected by 10 microM U73122. These studies indicate that U73122 is a relatively specific inhibitor of G-protein-mediated phospholipase C activation in pancreatic acini. In fura-2-loaded acini, U73122 inhibited the increases in [Ca2+]i stimulated by these high concentrations of secretagogues which can be demonstrated to elicit PI turnover. The [Ca2+]i signal generated by directly stimulating G-proteins with sodium fluoride was also inhibited by U73122; however, the [Ca2+]i rise induced by thapsigargin was unaffected. These data indicate that the mechanism of inhibition was distal to the occupation of cell surface receptors but did not involve an interference of Ca2+ metabolism in general. When [Ca2+]i oscillations were elicited by low concentrations of cholecystokinin or carbachol, U73122 rapidly inhibited the oscillating [Ca2+]i signal. In contrast, oscillations induced by an analogue of cholecystokinin, JMV-180, which does not stimulate changes in PI metabolism at any concentration, were unaffected. This indicates that cholecystokinin- and carbachol-induced oscillations are probably initiated by small, localized changes in PI metabolism, which are not readily detectable. However, the inability of U73122 to inhibit JMV-180-induced oscillations indicates that PI metabolism may not necessarily be a prerequisite for the generation of [Ca2+]i oscillations.