肾小管基底侧钠/二羧基转运蛋白随增龄的表达变化

目的：观察大鼠及人类肾小管基底侧钠/二羧基转运蛋白（NaCD3）随增龄的表达变化规律,并探讨其在肾脏衰老变化中的意义。方法：采用Northern杂交、Western印迹免疫组化染色方法,从基因及蛋白质水平观察大鼠出生后1d、7d、1个月、3、12、24个月及少年、中青年、老年正常人肾组织NaDC3表达变化趋势,并利用生化方法测定大鼠血、尿枸椽酸。结果：（1）大鼠血及尿枸椽酸浓度随鼠龄增长呈现逐渐下降的趋势。（2）大鼠肾组织Northern杂交及Western印迹结果显示随鼠龄增长NaDC3mRNA及蛋白表达逐渐增强的趋势。（3）免疫组化结果显示NaDC3表达于大鼠及人肾脏近端小管基底侧,从大鼠出生后7d开始表达,后随鼠龄增长表达逐渐增强;在人类随年龄增长也呈现表达逐渐增强的趋势。结论：NaDC3可能通过枸椽酸等物质的能量代谢机制参与了机体的衰老过程。

Na+/dicarboxylate cotransporter expression changed with aging in basolateral membrane of the renal tubular epithelial cells

OBJECTIVE: To study the change with aging of Na(+)/dicarboxylate cotransporter (NaDC3) expression in basolateral membrane of epithelial cell in proximal renal tubules in rat and human being. METHODS: Six groups of 6 Wistar rats at the age of: 1 day, 7 days, 1 month, 3 months, 12 months, and 24 months respectively were killed and their kidneys were taken to be examined immunohistochemically. Samples of kidney from 15 normal human beings, 5 in the group aged 6 - 8, 5 in the group aged 32 - 44, and 5 in the group aged 63 - 65, were examined immunohistochemically. Northern blotting, and Western blotting were used to detect the mRNA and protein expression of NaDC3 in renal tissues from both rats and human beings. The concentrations of citrate in both plasma and urine of the rats were tested. RESULTS: (1) The concentration of citrate in urine was340 mg/L +/- 144 mg/L in rats at the age of 7 days and declined gradually with aging significantly to the value of 59 mg/L +/- 27 mg/L in the rats aged 24 months (P < 0.05). The concentration of citrate in rat plasma was 85 mg/L +/- 45 mg/L and then declined gradually with aging significantly to the value of 31 mg/L +/- 20 mg/L at the age of 24 months (P < 0.05). (2) The renal expression of both mRNA and protein of NaDC3 increased with aging in rats and human beings (P < 0.01). (3) Located in the basolateral membrane of epithelial cell in the proximal renal tubule, NaDC3 expression began to be detected in rat since at the age of 7 days and then increased gradually in comparison with that at the day 7 (P < 0.01). However, the value of NaDC3 expression at the age of 24 months was not significantly different from that at the age of 12 months (P > 0.05). Similar results were also observed in normal human beings. CONCLUSION: NaDC3 may play a role in the aging process through the metabolic mechanism of citrate, etc.