Seyama I, Yamada K, Kato R, Masutani T, Hamada M
Department of Physiology, School of Medicine, Hiroshima University, Japan.
Biophys J. 1988 Feb;53(2):271-4. doi: 10.1016/S0006-3495(88)83088-1.
External application of alpha-dihydro-grayanotoxin II (alpha-H2-GTX II) to squid giant axon under nonperfused condition caused substantial membrane depolarization. Intracellular perfusion of the fibers retarded this depolarization appreciably. Tritium-labeled alpha-dihydro-grayanotoxin II ([3H]alpha-H2-GTX II) in the external medium can permeate through the cell membrane, but permeation of alpha-H2-GTX II does not occur either with the carrier-mediated system or through the pores of the Na channel. The finding that the most hydrophilic grayanotoxin analogue, desacyl asebotoxin VII, is effective only when applied internally, strongly suggests that the receptor for grayanotoxin does not exist on the external surface of the membrane. The linear relationship between the concentration of [3H]alpha-H2-GTX II in the external medium and the count in the effluent from the perfused axon indicates that GTX II diffuses through the cell membrane's lipid phase and reaches the site of action only approached from the internal medium.
在非灌注条件下，将α-二氢灰毒素II（α-H2-GTX II）施加于枪乌贼巨大轴突会引起明显的膜去极化。对纤维进行细胞内灌注可显著延缓这种去极化。外部介质中的氚标记α-二氢灰毒素II（[3H]α-H2-GTX II）能够透过细胞膜，但α-H2-GTX II既不是通过载体介导系统也不是通过钠通道的孔进行渗透。最具亲水性的灰毒素类似物脱酰基asebotoxin VII仅在内部施加时才有效，这一发现强烈表明灰毒素的受体不存在于膜的外表面。外部介质中[3H]α-H2-GTX II的浓度与灌注轴突流出物中的计数之间的线性关系表明，GTX II通过细胞膜的脂质相扩散，并且仅从内部介质接近作用位点。
