Hormonal stimulation of phosphatidylinositol breakdown with particular reference to the hepatic effects of vasopressin.
Hormonal stimulation of phosphatidylinositol breakdown with particular reference to the hepatic effects of vasopressin.
复制标题
磷脂酰肌醇分解的激素刺激，特别是加压素的肝脏作用。
DOI：
10.1042/bst0070861
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发表时间：
1979
影响因子：
3.9
通讯作者：
M. Billah
中科院分区：
文献类型：
--
作者：
R. H. Michell;Christopher J. Kirk;M. Billah
刺激磷脂酰肌醇分解，随后进行代偿性再合成，是多种细胞对多种激素和神经递质的反应。直到最近，大多数关于这种反应的工作都采用了分泌组织、神经组织或平滑肌，研究最深入的刺激是毒蕈碱、胆碱能和α-肾上腺素能刺激。作为所有这些过去研究的初步综合，我们得出了这样的观点：存在一个细胞表面受体家族，它们都作用于其靶细胞，导致胞质 Ca2+ 浓度升高。我们认为磷脂酰肌醇分解可能是这些受体引起 Ca2+ 动员的某种单一机制固有的反应（Michell, 1975, 1979a,b,c；Michell 等人，1977；Jones 等人[., 1979）。在其最普遍的解释中，该假设预测磷脂酰肌醇分解（以及其次是其再合成）的刺激应始终伴随激素刺激的 Ca2+ 动员。由于大多数刺激磷脂酰肌醇代谢的研究之前都使用组织碎片，因此在分离的肝细胞中测试这一预测似乎是合适的，分离的肝细胞是一种分散的细胞系统，适合多种类型的生化研究。因此，我们已经证明，暴露于三种糖原分解激素的离体大鼠肝细胞中磷脂酰肌醇代谢受到刺激，这些激素的作用似乎是由 Ca2+ 离子介导的，即加压素、血管紧张素和肾上腺素通过 a-受体发挥作用（Kirk 等人，1977、1978、1979；Billah 和 Michell，1978、1979）：可能性 De Torrentegui & Berthet (1966) 之前曾提出可能存在这样的α-肾上腺素能反应。对α-肾上腺素能拮抗剂和血管紧张素拮抗剂的研究表明，这三种激素作用于三种不同的受体（Kirk 等人，1977 年；Billah 和 Michell，1978 年、1979 年）。胰高血糖素是另一种糖原分解激素，但其作用是通过环磷酸腺苷介导的，对肝切片或肝细胞中的磷脂酰肌醇代谢没有影响（De Torrentegui & Berthet，1966；Kirk 等，1977）。肝细胞的磷脂酰肌醇反应最初被检测为32Pi掺入到与这些激素在生理缓冲液中孵育的细胞的磷脂酰肌醇中的刺激。然而，与其他细胞对适当配体的反应一样（Jones 等人，1979），这些反应中的起始反应似乎是磷脂酰肌醇分解；这已被检测为细胞磷脂酰肌醇含量的减少或预标记细胞磷脂酰肌醇中 32P 或 3H 的损失（Billah & Michell，1978，1979；C. J. Kirk，未发表的作品）。快速刺激磷脂酰肌醇代谢；添加加压素或血管紧张素后 1-2 分钟内即可清楚地观察到刺激标记（Billah & Michell，1979；Kirk 等人，1977），并且可以在 5 分钟内轻松检测到刺激分解（C. J. Kirk，未发表的工作）。尽管大鼠肝细胞对加压素、血管紧张素和α-肾上腺素能刺激的糖原分解反应似乎都涉及Caz+，但磷脂酰肌醇反应似乎独立于激素诱导的胞质Ca2+浓度变化而发生。两个观察结果得出了这个结论：(a) 磷脂酰肌醇分解和标记都对细胞 Ca2+ 剥夺具有抵抗力，至少是部分抵抗力； (b) CaZ+ 与离子载体 A23 187 一起进入肝细胞不会引起这些反应（Kirk 等，1978；Billah 和 Michell，1978，1979）。柯克等人。 (1979) 使用七种加压素样肽来研究参与刺激肝磷酸化酶的受体的配体选择性
Stimulated phosphatidylinositol breakdown, followed by compensatory resynthesis, is a response of a wide variety of cells to many hormones and neurotransmitters. Until recently, most work on this response employed secretory tissues, nervous tissues or smooth muscles, and the most intensively studied stimuli were muscarinic, cholinergic and a-adrenergic. As a tentative synthesis of all of these past studies, we have developed the view that there is a family of cell-surface receptors that all act upon their target cells to cause a rise in the cytosolic Ca2+ concentration. We suggested that phosphatidylinositol breakdown might be a reaction intrinsic to some unitary mechanism whereby these receptors bring about Ca2+ mobilization (Michell, 1975, 1979a,b,c; Michell et al., 1977; Jones et a[., 1979). In its most general interpretation, this hypothesis predicts that stimulation of phosphatidylinositol breakdown (and, secondarily, its resynthesis) should always accompany hormone-stimulated Ca2+ mobilization. Since the majority of studies of stimulated phosphatidylinositol metabolism have previously used tissue fragments, it seemed appropriate to test this prediction in isolated hepatocytes, a dispersed cell system that is amenable to many types of biochemical investigation. We have therefore demonstrated stimulation of phosphatidylinositol metabolism in isolated rat hepatocytes exposed to three glycogenolytic hormones whose actions appear to be mediated by Ca2+ ions, namely vasopressin, angiotensin and adrenaline acting through a-receptors (Kirk et al., 1977, 1978, 1979; Billah & Michell, 1978, 1979): the possibility that there might be such an a-adrenergic response was previously suggested by De Torrentegui & Berthet (1966). Studies with an a-adrenergic antagonist and an angiotensin antagonist have established that the three hormones act at three different receptors (Kirk et al., 1977; Billah & Michell, 1978, 1979). Glucagon, another hormone that is glycogenolytic but whose actions are mediated through cyclic AMP, had no effect on phosphatidylinositol metabolism in either liver slices or hepatocytes (De Torrentegui & Berthet, 1966; Kirk et af., 1977). The phosphatidylinositol responses of hepatocytes were initially detected as a stimulation of 32Pi incorporation into the phosphatidylinositol of cells incubated with these hormones in a physiological buffer. However, as with the responses of other cells to appropriate ligands (Jones et al., 1979), the initiating reaction in these responses appears to be phosphatidylinositol breakdown; this has been detected as a decrease in cellular phosphatidylinositol content or as a loss of 32P or 3H from the phosphatidylinositol of prelabelled cells (Billah & Michell, 1978, 1979; C. J. Kirk, unpublished work). Stimulation of phosphatidylinositol metabolism is rapid; stimulated labelling is clearly observed within 1-2min after addition of vasopressin or angiotensin (Billah & Michell, 1979; Kirk et af., 1977) and stimulated breakdown can readily be detected within 5min (C. J. Kirk, unpublished work). Although the glycogenolytic responses of rat hepatocytes to vasopressin, angiotensin and a-adrenergic stimuli all seem to involve Caz+, the phosphatidylinositol response appears to occur independently of hormone-induced changes in cytosolic Ca2+ concentration. Two observations lead to this conclusion: (a) phosphatidylinositol breakdown and labelling are both resistant, at least partially, to cellular Ca2+ deprivation ; (b) admission of CaZ+ into hepatocytes with the ionophore A23 187 brings about neither of these responses (Kirk et af., 1978; Billah & Michell, 1978, 1979). Kirk et al. (1979) used seven vasopressin-like peptides to investigate the ligand selectivity of the receptors involved in stimulation of hepatic phosphorylase and