Foulkes E C, Blanck S
Department of Environmental Health, University of Cincinnati College of Medicine, Ohio 45267-0056.
Proc Soc Exp Biol Med. 1993 Mar;202(3):302-6. doi: 10.3181/00379727-202-43539.
The intracellular volume of distribution of the nonmetabolizable sugar derivative 3-O-methylglucose was determined in the renal cortex of diuresing rabbits. This sugar is not well reabsorbed from the lumen, but is readily taken up across the basolateral cell membranes by an apparently flow-limited, nonconcentrative process. The ratio of distribution volumes of nonfiltered 3-O-methylglucose and inulin, therefore, equals the ratio of their mean artery-vein transit times. An intracellular and presumably cytoplasmic volume for 3-O-methylglucose of 0.13 ml/g was thus determined in the cortex of rabbits undergoing mannitol diuresis; similar values were obtained with three other less direct approaches. Availability of a reliable value permitted calculation of the activity gradients against which para-aminohippurate and the neutral amino acid cycloleucine can be accumulated at the basolateral membrane in vivo; both gradients equal about 6:1. This finding underlines the active nature of basolateral amino acid uptake and points to a further characteristic common to the organic anion and the cycloleucine carrier systems.
在进行利尿的兔肾皮质中，测定了不可代谢糖衍生物3 - O - 甲基葡萄糖的细胞内分布容积。这种糖不易从管腔中重吸收，但能通过一个明显受流量限制的非浓缩过程，很容易地跨基底外侧细胞膜被摄取。因此，未滤过的3 - O - 甲基葡萄糖与菊粉的分布容积之比，等于它们在平均动脉 - 静脉中的转运时间之比。由此在接受甘露醇利尿的兔皮质中确定了3 - O - 甲基葡萄糖的细胞内（大概是细胞质）容积为0.13 ml/g；通过其他三种不太直接的方法也得到了类似的值。有了可靠的值，就可以计算对氨基马尿酸盐和中性氨基酸环亮氨酸在体内基底外侧膜上积累时所对抗的活性梯度；这两种梯度均约为6:1。这一发现强调了基底外侧氨基酸摄取的主动性质，并指出了有机阴离子和环亮氨酸载体系统的另一个共同特征。
