Roth K S, Serabian M, Medow M S
Metabolism. 1982 Apr;31(4):406-10. doi: 10.1016/0026-0495(82)90118-4.
The developmental aspects of the renal uptake of 3-OH-3-CH3-glutaric acid (HMG) was examined using isolated renal tubules prepared from both newborn and adult rats and isolated renal brush border membranes vesicles from adult rats. The accumulation of 70 microM HMG by both newborn and adult tubules reached a steady state and achieved a distribution ratio (DR) of 4.9 and 6.5, respectively; decreased DR's at higher substrate concentrations suggest concentration-dependent uptake. Lineweaver-Burk analysis of the 5 min calculated velocities of HMG uptake by newborn and adult tubules indicate a single transport system with the same apparent Km of 0.2 mM in both age groups. The Vmax in adult rats was twofold greater than in newborn (0.95 versus 0.44 mM/1/5 min). The carrier system for HMG is assumed to be distinct from those of amino acids and sugars because tubule uptake of HMG is not affected by the presence of alpha-NH2-isobutyric acid and alpha-methyl-D-glucoside. Sodium maleate and acetoacetate significantly decreased HMG uptake in tubules of both age groups. HMG uptake by isolated renal brush border membrane vesicles from adult rats suggests that uptake is both carrier-mediated and Na+-dependent. These observations are consistent with renal tubular HMG uptake by an energy-dependent, carrier-mediated system.
使用从新生大鼠和成年大鼠制备的离体肾小管以及成年大鼠的离体肾刷状缘膜囊泡，研究了3-羟基-3-甲基戊二酸（HMG）肾脏摄取的发育方面。新生和成年肾小管对70μM HMG的积累均达到稳态，分布比（DR）分别为4.9和6.5；在较高底物浓度下DR降低表明存在浓度依赖性摄取。对新生和成年肾小管5分钟计算的HMG摄取速度进行Lineweaver-Burk分析表明，两个年龄组均存在单一转运系统，表观Km相同，均为0.2 mM。成年大鼠的Vmax比新生大鼠高两倍（0.95对0.44 mM/1/5分钟）。假定HMG的载体系统与氨基酸和糖的载体系统不同，因为HMG的肾小管摄取不受α-氨基异丁酸和α-甲基-D-葡萄糖苷的影响。马来酸钠和乙酰乙酸显著降低了两个年龄组肾小管中HMG的摄取。成年大鼠离体肾刷状缘膜囊泡对HMG的摄取表明，摄取是载体介导的且依赖于Na+。这些观察结果与能量依赖的载体介导系统对肾小管HMG的摄取一致。
