Tatsumi M, Takahashi M, Ohizumi Y
Mol Pharmacol. 1984 May;25(3):379-83.
Palytoxin, isolated from the zoanthid Palytoha species, is one of the most potent marine toxins. Palytoxin (1 nM-1 microM) caused a release of [3H]norepinephrine from clonal rat pheochromocytoma cells in a concentration-dependent manner. This releasing action of palytoxin was markedly inhibited or abolished by Co2+ or Ca2+ -free medium, but was not modified by tetrodotoxin. The release of [3H]norepinephrine induced by a low concentration (30 nM) of palytoxin was abolished in sodium-free medium and increased as the external Na+ concentrations were increased from 3 to 100 nM, but the release induced by a high concentration (1 microM) was unaffected by varying the concentration of external Na+ from 0 to 100 mM. The release of [3H]norepinephrine induced by both concentrations of palytoxin increased with increasing Ca2+ concentrations from 0 to 3 mM. Palytoxin caused a concentration-dependent increase in 22Na and 45Ca influxes into pheochromocytoma cells at concentrations of 0.1 nM-10 nM and 1 nM-1 microM, respectively. The palytoxin-induced 45Ca influx was markedly inhibited by Co2+, whereas the palytoxin-induced 22Na influx was not affected by tetrodotoxin. These results suggest that in pheochromocytoma cells the [3H]norepinephrine release induced by lower concentrations of palytoxin is primarily brought about by increasing tetrodotoxin-insensitive Na+ permeability across the cell membrane, whereas that induced by higher concentrations is mainly caused by a direct increase in Ca2+ influx into them.
从群体海葵（Palytoha属）中分离出的岩沙海葵毒素是最具毒性的海洋毒素之一。岩沙海葵毒素（1纳摩尔至1微摩尔）以浓度依赖的方式促使克隆化大鼠嗜铬细胞瘤细胞释放[3H]去甲肾上腺素。岩沙海葵毒素的这种释放作用在无钴离子或无钙离子的培养基中受到显著抑制或消除，但不受河豚毒素的影响。低浓度（30纳摩尔）岩沙海葵毒素诱导的[3H]去甲肾上腺素释放在无钠培养基中被消除，并且随着外部钠离子浓度从3纳摩尔增加到100纳摩尔而增加，但高浓度（1微摩尔）诱导的释放不受外部钠离子浓度从0到100毫摩尔变化的影响。两种浓度的岩沙海葵毒素诱导的[3H]去甲肾上腺素释放均随着钙离子浓度从0增加到3毫摩尔而增加。岩沙海葵毒素分别在0.1纳摩尔至10纳摩尔和1纳摩尔至1微摩尔的浓度下导致嗜铬细胞瘤细胞中22钠和45钙的内流呈浓度依赖性增加。岩沙海葵毒素诱导的45钙内流受到钴离子的显著抑制，而岩沙海葵毒素诱导的22钠内流不受河豚毒素的影响。这些结果表明，在嗜铬细胞瘤细胞中，较低浓度岩沙海葵毒素诱导的[3H]去甲肾上腺素释放主要是通过增加细胞膜对河豚毒素不敏感的钠离子通透性实现的，而较高浓度诱导的释放主要是由钙离子直接内流增加引起的。
