Zeidler R B, Lee P, Kim H D
J Gen Physiol. 1976 Jan;67(1):67-80. doi: 10.1085/jgp.67.1.67.
The glucose-permeable fetal red cells in the pig are entirely replaced by glucose-impermeable adult red cells within a month after birth. This study investigates the kinetic parameters of the glucose transport mechanism in newborn pig red cells in comparison with immature adult red cells (reticulocytes) as well as the fully matured adult erythrocytes. Influx and efflux of the nonmetabolizable 3-O-methyl glucose (3-O-M-G) in red cells of newborn pigs saturate at high substrate concentrations and exhibit typical Michaelis-Menten kinetics. Km values for efflux are 15.2 and 18.2 mM for 15 and 22 degrees C, respectively. Q10 computed between 10 and 26 degrees is 5.0. The energy of activation for the transport process is 34,000 cal mol-1. The effectiveness of hexoses in competing with 3-O-M-G in efflux is in the following order: D-glucose greater than D-mannose greater than D-fructose greater than D-galactose. Efflux of 3-O-M-G does not increase with 3-O-M-G or D-ribose in the medium and is reduced by 2,4-dinitroflurobenzene (DNFB), p-chloromercuriphenyl sufonic acid (PCMBS), and phloridzin. The reticulocytes are shown to possess a carrier-mediated transport but with a considerably lower transport rate. As the reticulocytes mature into normal red cells, the carrier transport mechanism is lost.
猪体内可透过葡萄糖的胎儿红细胞在出生后一个月内会完全被不可透过葡萄糖的成年红细胞所取代。本研究调查了新生猪红细胞中葡萄糖转运机制的动力学参数，并与未成熟的成年红细胞（网织红细胞）以及完全成熟的成年红细胞进行了比较。新生猪红细胞中不可代谢的3 - O - 甲基葡萄糖（3 - O - M - G）的流入和流出在高底物浓度下达到饱和，并呈现典型的米氏动力学。在15℃和22℃时，流出的Km值分别为15.2 mM和18.2 mM。在10℃至26℃之间计算的Q10为5.0。转运过程的活化能为34,000卡/摩尔。己糖在与3 - O - M - G竞争流出时的有效性顺序如下：D - 葡萄糖＞D - 甘露糖＞D - 果糖＞D - 半乳糖。3 - O - M - G在培养基中的流出量不会因3 - O - M - G或D - 核糖而增加，并且会被2,4 - 二硝基氟苯（DNFB）、对氯汞苯磺酸（PCMBS）和根皮苷降低。结果表明网织红细胞具有载体介导的转运，但转运速率相当低。随着网织红细胞成熟为正常红细胞，载体转运机制会丧失。
