MOLECULAR-BASIS OF OSMOTIC REGULATION
MOLECULAR-BASIS OF OSMOTIC REGULATION
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DOI：
10.1152/ajprenal.1995.268.6.f983
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发表时间：
1995-06-01
期刊：
影响因子：
--
通讯作者：
BURG, MB
中科院分区：
文献类型：
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作者：
BURG, MB
细胞几乎普遍通过积累相容的有机渗透压物质来响应长期高渗压的应激。这使得它们能够保持正常的细胞体积，而不会有害地增加细胞内无机离子浓度。肾内髓质中的细胞暴露于可变浓度的盐和尿素，其可达到摩尔浓度水平。它们积累的有机渗透物包括山梨糖醇、甜菜碱、肌醇、牛磺酸和甘油磷酸胆碱（GPC）。这篇综述考虑了最近的进展，了解这些物质的渗透调节。山梨糖醇是由葡萄糖在醛糖还原酶的催化下合成的。高渗通过增加其基因的转录来提高这种酶的丰度。甜菜碱是通过一种特殊的转运体吸收的。高渗通过增加转运蛋白的转录来增加转运蛋白的数量。目前的研究表明，侧接醛糖还原酶和甜菜碱转运蛋白基因的5'区含有渗透反应元件，其响应于高渗而增加转录。肌醇和牛磺酸摄取的渗透调节也涉及特定转运蛋白基因表达的增加。GPC的独特之处在于其水平响应于高尿素以及高渗而升高。GPC的积累主要受其降解为胆碱的变化的调节，由GPC催化：胆碱磷酸二酯酶。许多其他基因，包括那些热休克蛋白，也诱导高渗。它们的调节及其在渗透调节中的作用是正在进行的大量研究的主题。
Cells almost universally respond to the stress of long-term hyperosmolality by accumulating compatible organic osmolytes. This allows them to maintain normal cell volume without a deleterious increase in intracellular inorganic ion concentration. Cells in the renal inner medulla are exposed to variable concentrations of salt and urea that may reach molal levels. The organic osmolytes that they accumulate include sorbitol, betaine, inositol, taurine, and glycerophosphocholine (GPC). This review considers recent advances in understanding osmotic regulation of these substances. Sorbitol is synthesized from glucose catalyzed by aldose reductase. Hypertonicity elevates the abundance of this enzyme by increasing transcription of its gene. Betaine is taken up via a specialized transporter. Hypertonicity raises the number of transporters by increasing their transcription. Current studies demonstrate that the 5' regions flanking the aldose reductase and betaine transporter genes contain osmotic response elements that increase transcription in response to hypertonicity. Osmotic regulation of inositol and taurine uptake also involves increased expression of specific transporter genes. GPC is unique in that its level rises in response to high urea, as well as hypertonicity. GPC accumulation is mainly regulated by changes in its degradation to choline, catalyzed by GPC:choline phosphodiesterase. Numerous other genes, including those for heat shock proteins, are also induced by hypertonicity. Their regulation and their role in osmotic regulation are the subject of considerable ongoing research.