Cessac A L, Perichon M, Schaeverbeke J, Bakala H
Laboratoire de Biologie Cellulaire, Université Paris VII, France.
Mech Ageing Dev. 1993 Aug 1;70(1-2):139-48. doi: 10.1016/0047-6374(93)90065-y.
A selective proteinuria occurs with normal aging. We investigated the contribution of a defect in the receptor-mediated endocytosis to the age-related albuminuria by measuring albumin binding by renal brush-border membrane vesicles from young and old female Wistar rats using a filtration method. Old (24 months) rats had a significantly higher proteinuria (13.29 +/- 5.25 mg prot/24 h/100 g bw) than did young (3 months) rats (1.23 +/- 0.55 mg prot/24 h/100 g bw). Scatchard analysis of the kinetic parameters of 125I-albumin binding revealed a decrease in the binding capacity of brush-border membrane vesicles from old rats. The number of binding sites, N (pmol/mg protein/min) was 236.84 +/- 97.50 in old rat preparations and 380.27 +/- 178.36 in young rat vesicles (P < 0.05). By contrast, Km did not change significantly with age (478.86 +/- 259.29 nM in old rat vesicles and 498.00 +/- 220.36 nM in young rat preparations). Consequently the index of adsorptive endocytosis efficiency (the N/Km ratio) decreased drastically with age from 0.782 +/- 0.238 at 3 months to 0.547 +/- 0.199 at 24 months (P < 0.05). These data indicate that defective receptor-mediated endocytosis could, at least partly, explain the age-dependent rise in urinary albumin excretion.
随着年龄正常增长会出现选择性蛋白尿。我们通过使用过滤法测量年轻和老年雌性Wistar大鼠肾刷状缘膜囊泡对白蛋白的结合情况，研究了受体介导的内吞作用缺陷对年龄相关性蛋白尿的影响。老年（24个月）大鼠的蛋白尿（13.29±5.25mg蛋白/24小时/100g体重）显著高于年轻（3个月）大鼠（1.23±0.55mg蛋白/24小时/100g体重）。对125I-白蛋白结合动力学参数的Scatchard分析显示，老年大鼠刷状缘膜囊泡的结合能力下降。老年大鼠制剂中结合位点的数量N（pmol/mg蛋白/分钟）为236.84±97.50，年轻大鼠囊泡中为380.27±178.36（P<0.05）。相比之下，Km随年龄变化不显著（老年大鼠囊泡中为478.86±259.29nM，年轻大鼠制剂中为498.00±220.36nM）。因此，吸附性内吞作用效率指数（N/Km比值）随年龄急剧下降，从3个月时的0.782±0.238降至
