Ferrier B, Martin M, Baverel G
Am J Physiol. 1985 Mar;248(3 Pt 2):F404-12. doi: 10.1152/ajprenal.1985.248.3.F404.
The transport of alpha-ketoglutarate (alpha-KG) across the luminal membrane of the rat nephron was studied by micropuncture and microassay techniques. In normal and acidotic rats, approximately 75% of the filtered alpha-KG was reabsorbed in the proximal tubule and 20% in the pars recta and/or loop of Henle at endogenous plasma concentration of alpha-KG. A progressive elevation to steady-state levels of plasma alpha-KG resulted in a progressive reduction of the fractional reabsorption of alpha-KG in the proximal tubule as well as in a progressive increase in the fractional reabsorption of alpha-KG in the pars recta and/or loop of Henle. At plasma alpha-KG concentration 20-40 times above normal, reabsorption of alpha-KG was found to be limited by a maximal tubular capacity. In alkalotic rats, net secretion of alpha-KG in the early proximal convoluted tubule, net reabsorption in the remainder of the proximal convoluted tubule, and net secretion in the pars recta and/or loop of Henle were observed. These micropuncture data indicate that, depending on the acid-base conditions, net reabsorption or net secretion of alpha-KG may occur in at least two distinct sites along the rat nephron.
采用微穿刺和微量分析技术研究了大鼠肾单位管腔膜对α-酮戊二酸（α-KG）的转运。在内源性血浆α-KG浓度下，正常和酸中毒大鼠中，约75%滤过的α-KG在近端小管被重吸收，20%在直部和/或髓袢被重吸收。血浆α-KG逐渐升高至稳态水平导致近端小管中α-KG的重吸收分数逐渐降低，以及直部和/或髓袢中α-KG的重吸收分数逐渐增加。在血浆α-KG浓度高于正常20 - 40倍时，发现α-KG的重吸收受最大肾小管转运能力限制。在碱中毒大鼠中，观察到近端曲管起始段有α-KG的净分泌，近端曲管其余部分有净重吸收，直部和/或髓袢有净分泌。这些微穿刺数据表明，根据酸碱条件，大鼠肾单位至少有两个不同部位可能发生α-KG的净重吸收或净分泌。
