期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：4
页码：2293-2297
DOI：10.1073/pnas.77.4.2293
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The turnover rates of junctional acetylcholine receptors were measured in innervated and denervated mouse sternomastoid neuromuscular junctions by 125I-labeled alpha-bungarotoxin binding. First, we determined that the density of labeled toxin initially bound to the neuromuscular junction was essentially unchanged up to 16 days after denervation. Innervated muscles and muscles that had been denervated 8 days previously were then saturated with labeled toxin, and the specific label at the endplate regions was compared by gamma counting 7 days later. At that time, the residual junctional label seen in innervated muscle was 3.2 times greater than in denervated muscle. Electron microscope autoradiography further showed that, after saturation with unlabeled toxin, new binding sites appeared rapidly at the specialized receptive region of the postsynaptic membrane with an apparent half-time of turnover of 2-3 days. At innervated junctions, the half-time of turnover was about 10 days. These data show that the mechanisms that control receptor turnover rates are different from those that control high-density receptor clustering. The slow turnover rate of junctional receptors appears to be more directly dependent on the presence of the nerve than is the clustering of junctional receptors.
