Tipnis U R, Malhotra S K
Cytobios. 1981;31(122):91-106.
A quantitative distribution of alpha-bungarotoxin (alpha-BGT) binding sites i.e. acetylcholine receptors (AchR) has been investigated and correlated with the distribution of intramembranous particles (approximately 15 nm in diameter) observed on the freeze-fractured face (P-face) of the non-synaptic sarcolemma of denervated muscle. By both light and electron microscopy autoradiography, randomly distributed clusters of alpha-BGT sites are visualized on the plasma membrane of the denervated muscle. Such distributions of the toxin binding sites correspond with that of the 15 nm particles on the P-face of the denervated muscle. Quantitative studies suggest that upon denervation the toxin binding sites increase approximately 60-fold in the non-synaptic sarcolemma. However, the density of these alpha-BGT sites is 4--5 times more than the density of the 15 nm particles. On the basis that there are two alpha-BGT binding sites per AchR molecule, these results suggest that each 15 nm particle is composed of more than one AchR receptor. In addition to the increase in toxin binding sites on the non-synaptic sarcolemma, a notable increase in the number of silver grains is observed in the peripheral sarcoplasm and is speculated to be part of the intracellular pool of receptors.
已对α-银环蛇毒素（α-BGT）结合位点即乙酰胆碱受体（AchR）的定量分布进行了研究，并将其与在失神经肌肉非突触肌膜的冷冻断裂面（P面）上观察到的膜内颗粒（直径约15nm）的分布相关联。通过光学显微镜和电子显微镜放射自显影术，在失神经肌肉的质膜上可看到α-BGT位点的随机分布簇。毒素结合位点的这种分布与失神经肌肉P面上15nm颗粒的分布相对应。定量研究表明，失神经后非突触肌膜中毒素结合位点增加约60倍。然而，这些α-BGT位点的密度比15nm颗粒的密度高4至5倍。基于每个AchR分子有两个α-BGT结合位点，这些结果表明每个15nm颗粒由不止一个AchR受体组成。除了非突触肌膜上毒素结合位点增加外，在外周肌浆中还观察到银颗粒数量显著增加，推测这是细胞内受体池的一部分。
