大鼠肾单位中谷氨酰胺蓄积及肾小管重吸收的定位

Localization of glutamine accumulation and tubular reabsorption in rat nephron.

作者信息

Burch H B, Chan A W, Alvey T R, Lowry O H

出版信息

Kidney Int. 1978 Nov;14(5):406-13. doi: 10.1038/ki.1978.145.

DOI:10.1038/ki.1978.145

Abstract

Glutamine accumulation in rat kidney was investigated by giving large loads of gluta, mate and aspartate and measuring glutamine changes in seven completely defined portions of the nephron and in small patches from the thin limb area and from the papilla. Both glutamate and aspartate (which is partly coverted to glutamate) caused increases up to sixfold in glutamine which were mainly confined to the proximal straight tubule. Plasma glutamine is minimally affected. In contrast, large glutamine loads doubled plasma glutamine and caused about a doubling of glutamine concentrations in all parts of the nephron, but resulted in no greater change in the proximal straight tubule than elsewhere. Simultaneous inulin and glutamine measurements make it seem likely that the proximal convoluted tubule is a major site of glutamine reabsorption. The low glutamine concentrations in these cells (only 40% higher than that in plasma) indicate a very small gradient at the antiluminal surface. We suggest that the proximal straight tubule is the major site of glutamine synthesis but that it may not be an important site of glutamine breakdown.

摘要

通过给予大鼠大量的谷氨酸盐和天冬氨酸盐，并测量肾单位七个完全确定部分以及来自细段区域和乳头的小片状组织中的谷氨酰胺变化，对大鼠肾脏中的谷氨酰胺积累进行了研究。谷氨酸盐和天冬氨酸盐（部分转化为谷氨酸盐）均使谷氨酰胺增加多达六倍，这主要局限于近端直小管。血浆谷氨酰胺受影响最小。相比之下，大量的谷氨酰胺负荷使血浆谷氨酰胺增加了一倍，并使肾单位各部分的谷氨酰胺浓度增加了约一倍，但近端直小管的变化并不比其他部位更大。同时进行的菊粉和谷氨酰胺测量表明，近端曲小管可能是谷氨酰胺重吸收的主要部位。这些细胞中谷氨酰胺浓度较低（仅比血浆中的高40%），表明在管腔反面的梯度非常小。我们认为近端直小管是谷氨酰胺合成的主要部位，但可能不是谷氨酰胺分解的重要部位。