Weinberg J M, Buchanan D N, Davis J A, Abarzua M
Department of Internal Medicine, University of Michigan, Ann Arbor.
J Am Soc Nephrol. 1991 Jan;1(7):949-58. doi: 10.1681/ASN.V17949.
To clarify the roles of butyrate and acylglycine formation in hypoxic proximal tubule cell injury and protection by glycine and to test the contribution of iodoacetate-suppressible metabolism to protection, (1) it was determined whether protection by glycine is fully expressed when glucose, lactate, alanine, and butyrate are replaced by alpha-ketoglutarate as the sole substrate for the tubules, (2) butyrate metabolism and acylglycine formation were directly measured in control and hypoxic preparations, and (3) it was assessed whether injury produced by iodoacetate, a potent inhibitor of glycolytic metabolism, is subject to protection by glycine. Susceptibility to hypoxic injury in medium with alpha-ketoglutarate as the sole substrate was similar to that seen in medium containing glucose, lactate, alanine, and butyrate. Tubules in alpha-ketoglutarate medium showed high degrees of protection by glycine against injury produced by 30-min of hypoxia, by iodoacetate alone, and by iodoacetate combined with hypoxia. Protection did not require preservation of cell ATP or glutathione. In glucose-lactate-alanine-butyrate medium, butyrate, measured by gas chromatography, was rapidly metabolized by oxygenated tubules and fully accounted for basal rates of oxygen consumption. Butyrate utilization stopped during hypoxia. Neither aspect of butyrate metabolism was altered by glycine. Formation of acylglycines was assessed by gas chromatography/mass spectroscopy. In preparations treated with glycine, butyrylglycine was detected under both oxygenated and hypoxic conditions; the quantities, however, were small and no other acylglycines were found. These observations indicate that protective effects of glycine are independent of short-chain acylglycine formation and glycolytic metabolism.
为阐明丁酸盐和酰基甘氨酸形成在缺氧近端小管细胞损伤及甘氨酸保护作用中的作用，并测试碘乙酸可抑制的代谢对保护作用的贡献，进行了以下实验：（1）确定当葡萄糖、乳酸、丙氨酸和丁酸盐被α-酮戊二酸替代作为小管的唯一底物时，甘氨酸的保护作用是否能充分表达；（2）直接测量对照和缺氧制剂中的丁酸盐代谢和酰基甘氨酸形成；（3）评估碘乙酸（一种糖酵解代谢的强效抑制剂）所致损伤是否受到甘氨酸的保护。以α-酮戊二酸作为唯一底物的培养基中对缺氧损伤的易感性与含有葡萄糖、乳酸、丙氨酸和丁酸盐的培养基中所见相似。α-酮戊二酸培养基中的小管对30分钟缺氧、单独碘乙酸以及碘乙酸与缺氧联合所致损伤均表现出高度的甘氨酸保护作用。这种保护作用不需要维持细胞ATP或谷胱甘肽。在葡萄糖-乳酸-丙氨酸-丁酸盐培养基中，通过气相色谱法测定，丁酸盐被有氧小管迅速代谢，且完全占基础耗氧率。缺氧时丁酸盐利用停止。丁酸盐代谢的这两个方面均未被甘氨酸改变。通过气相色谱/质谱法评估酰基甘氨酸的形成。在用甘氨酸处理的制剂中，在有氧和缺氧条件下均检测到丁酰甘氨酸；然而，其含量很少，未发现其他酰基甘氨酸。这些观察结果表明，甘氨酸的保护作用独立于短链酰基甘氨酸形成和糖酵解代谢。
