Mader S L, Downing C L, Amos-Landgraf J, Swebjka P
VA Medical Center and Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
J Gerontol A Biol Sci Med Sci. 1996 Mar;51(2):B111-6. doi: 10.1093/gerona/51a.2.b111.
Blood vessels from aged animals and humans have impaired relaxation to beta-adrenergic stimulation. We hypothesized that a loss of stimulatory G protein (Gs) or an increase in inhibitory G proteins (Gi) could explain this impairment. Aortic membranes from Fischer 344 rats of 4 age groups (6 week to 24 month) were studied. G-protein levels were initially assessed using cholera and pertussis toxin labeling. There was a marked decline in cholera toxin labeling (which primarily labels Gs alpha) from 6 weeks to 6 months which persisted in 12-month and 24-month animals. Pertussis toxin labeling (which primarily labels Gi alpha) showed only a slight decline with age. Western blotting was performed using specific antibodies for the alpha subunit of Gs, Gi1&2, Gi3, and G beta. There was no significant change in Gs alpha, Gi alpha, or G beta protein levels with age. We conclude there is a loss of cholera toxin-catalyzed ADP ribosylation with age, which does not represent a loss of the stimulatory alpha subunit of G protein. These data suggest that the loss of cholera toxin labeling seen with age may be a marker for loss of Gs alpha function.
来自老年动物和人类的血管对β-肾上腺素能刺激的舒张功能受损。我们推测，刺激性G蛋白（Gs）的丧失或抑制性G蛋白（Gi）的增加可能解释这种损害。对4个年龄组（6周龄至24月龄）的Fischer 344大鼠的主动脉膜进行了研究。最初使用霍乱毒素和百日咳毒素标记来评估G蛋白水平。从6周龄到6月龄，霍乱毒素标记（主要标记Gsα）显著下降，这种下降在12月龄和24月龄的动物中持续存在。百日咳毒素标记（主要标记Giα）仅随年龄略有下降。使用针对Gs、Gi1&2、Gi3和Gβα亚基的特异性抗体进行蛋白质免疫印迹分析。随着年龄的增长，Gsα、Giα或Gβ蛋白水平没有显著变化。我们得出结论，随着年龄增长，霍乱毒素催化的ADP核糖基化会丧失，但这并不代表G蛋白刺激性α亚基的丧失。这些数据表明，随着年龄增长出现的霍乱毒素标记丧失可能是Gsα功能丧失的一个标志。
