Mechanism of palytoxin-induced Na+ influx into cultured bovine adrenal chromaffin cells: possible involvement of Na+/H+ exchange system.
To elucidate the mechanism of palytoxin (PTX)-induced Na+ influx, we examined the effect of amiloride, an inhibitor of Na+/H(+)-antiporter, on PTX-induced Na+ influx into cultured bovine adrenal chromaffin cells in relation to its effects on Ca2+ influx and catecholamine secretion. Amiloride dose-dependently inhibited PTX-induced 22Na+ influx, whereas tetrodotoxin (TTX) had no effect. Amiloride also inhibited PTX-induced Na(+)-dependent 45Ca2+ influx and catecholamine secretion. PTX alone did not significantly affect the intracellular pH, but it decreased in the presence of PTX and amiloride. These results indicate that an amiloride-sensitive Na+/H+ exchange mechanism is probably involved in PTX-induced, TTX-insensitive Na+ influx that triggers Ca2+ influx and catecholamine secretion from the cells.
Department of Pharmacology, Tokushima University School of Medicine, Tokushima, Japan.
M
M
Yoshizumi
H
H
Houchi
Y
Y
Ishimura
Y
Y
Masuda
K
K
Morita
M
M
Oka
D000178:Acrylamides; D000311:Adrenal Glands / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D002838:Chromaffin System / Q000166:cytology* / Q000187:drug effects; D003064:Cnidarian Venoms / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology; D000095702:Polyether Toxins
D000178:Acrylamides; D000584:Amiloride; D002118:Calcium; D002352:Carrier Proteins; D003064:Cnidarian Venoms; D015222:Sodium Channels; D017923:Sodium-Hydrogen Exchangers; D013779:Tetrodotoxin; D014701:Veratridine; C010272:palytoxin; D000095702:Polyether Toxins