MECHANISM OF PALYTOXIN-INDUCED [H-3]NOREPINEPHRINE RELEASE FROM A RAT PHEOCHROMOCYTOMA CELL-LINE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 25  (3) , 379-383
Abstract
Palytoxin, isolated from the zoanthid Palytoha, is 1 of the most potent marine toxins. Palytoxin (1 nM-1 .mu.M) 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 Na-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 .mu.M) 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 0.1-10 nM and 1 nM-1 .mu.M, respectively. The palytoxin-induced 45Ca influx was markedly inhibited by Co2+; the palytoxin-induced 22Na influx was not affected by tetrodotoxin. In pheochromocytoma cells the [3H]norepinephrine release induced by lower concentrations of palytoxin was primarily brought about by increasing tetrodotoxin-insensitve Na+ permeability across the cell membrane; that induced by higher concentrations was mainly caused by a direct increase in Ca2+ influx into them.

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