Nord E, Wright S H, Kippen I, Wright E M
Am J Physiol. 1982 Nov;243(5):F456-62. doi: 10.1152/ajprenal.1982.243.5.F456.
Brush border membrane vesicles were purified from rabbit renal cortex using a calcium-precipitation procedure, and the uptake of carboxylic acids was determined by a rapid-filtration method. L-Lactate, pyruvate (monocarboxylic acids), and succinate (dicarboxylic acid) demonstrated features of Na+ cotransport: enhanced initial rate (1 s) of uptake with an inward Na+ gradient compared with the Na+ -free control condition and transient accumulation of substrate within the vesicles. Kinetic parameters derived for L-lactate and succinate show that each substrate is transported via single pathway and that the two substrates exhibit marginal cross-inhibition. A range of monocarboxylic acids including pyruvate and ketone bodies appear to interact with the monocarboxylic acid carrier. The kinetics of Nat-dependent pyruvate uptake suggest at least two transport pathways-namely, that this monocarboxylate shares both the mono- and dicarboxylic acid carriers. We conclude that isolated rabbit renal microvillus membranes possess independent transport systems for mono- and polycarboxylic acids.
采用钙沉淀法从兔肾皮质中纯化刷状缘膜囊泡，并用快速过滤法测定羧酸的摄取。L-乳酸、丙酮酸（一元羧酸）和琥珀酸（二元羧酸）表现出Na⁺协同转运的特征：与无Na⁺对照条件相比，在存在内向Na⁺梯度时摄取的初始速率（1秒）增强，且底物在囊泡内短暂积累。L-乳酸和琥珀酸的动力学参数表明，每种底物都通过单一途径转运，且两种底物表现出轻微的交叉抑制。包括丙酮酸和酮体在内的一系列一元羧酸似乎与一元羧酸载体相互作用。Na⁺依赖性丙酮酸摄取的动力学表明至少有两条转运途径，即这种一元羧酸盐同时共享一元和二元羧酸载体。我们得出结论，分离的兔肾微绒毛膜具有独立的一元和多元羧酸转运系统。
