Mooradian A D, Morin A M, Cipp L J, Haspel H C
Tucson VA Medical Center, University of Arizona College of Medicine 85719.
Brain Res. 1991 Jun 14;551(1-2):145-9. doi: 10.1016/0006-8993(91)90926-m.
To determine the biochemical basis of decreased brain uptake of glucose with age, the brain influx of 3-O-methylglucose (3-O-MG) was measured in male Fischer 344 rats at various ages using the arterial injection-tissue sampling technique of Oldendorf. The Vmax of 3-O-MG transport in the 24-month-old rats (0.22 +/- 0.14 mumol/min/g) was significantly lower than that in 3-month-old rats (0.88 +/- 0.18 mumol/min/g) (P less than 0.05). The Km of transport in aged rats (10.1 +/- 4.8 mM) was not different from that in young rats (8.1 +/- 2.5 mM). The cytochalasin B binding sites in cerebral microvessels isolated from aged rats (13.9 +/- 0.9 pmol/mg) compared to the binding sites in cerebral microvessels of young rats (21.9 +/- 1.4 pmol/mg) were significantly reduced (P less than 0.001). However, the immunoreactive mass of glucose transporter of cerebral microvessels was not altered with age. The enrichment of capillary preparations with gamma-glutamyl transpeptidase activity, a marker of endothelial cells, was not altered in aged rats, suggesting that the reduced blood-brain barrier transport of glucose is due to specific reduction in glucose binding sites of the transporter rather than secondary to a non-specific age-related effect of endothelial cell drop-out.
为了确定随着年龄增长大脑葡萄糖摄取减少的生化基础，使用奥尔登多夫的动脉注射-组织采样技术，在不同年龄的雄性费希尔344大鼠中测量了3-O-甲基葡萄糖（3-O-MG）的脑内流入量。24月龄大鼠中3-O-MG转运的Vmax（0.22±0.14μmol/分钟/克）显著低于3月龄大鼠（0.88±0.18μmol/分钟/克）（P<0.05）。老年大鼠转运的Km（10.1±4.8mM）与年轻大鼠（8.1±2.5mM）无差异。与年轻大鼠脑微血管中的结合位点（21.9±1.4pmol/毫克）相比，老年大鼠分离的脑微血管中细胞松弛素B结合位点（13.9±0.9pmol/毫克）显著减少（P<0.001）。然而，脑微血管葡萄糖转运蛋白的免疫反应量并未随年龄改变。作为内皮细胞标志物的γ-谷氨酰转肽酶活性在老年大鼠中未改变，这表明葡萄糖血脑屏障转运减少是由于转运蛋白的葡萄糖结合位点特异性减少，而非继发于内皮细胞丢失的非特异性年龄相关效应。
