Abstract
The effect of palytoxin (C 129H 223N 3O 54) on Ca 2+ homeostasis in immune cells has not been studied. Therefore, we investigated the effect of palytoxin on the cytosolic-free Ca 2+ concentration ([Ca 2+] i ) in mouse spleen cells using a fluorescence Ca 2+ indicator, fura-2. Palytoxin (0.1–100 nM) increased [Ca 2+] i in a concentration-dependent manner. The palytoxin-induced increase in [Ca 2+] i was abolished by the omission of extracellular Ca 2+ or 1-[β-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF-96365, 100 μM), and was greatly inhibited by Ni 2+ (2 mM). Ouabain (0.5–1 mM) partially inhibited the palytoxin-induced response. There was no effect of decreased extracellular Na + (6.2 mM), tetrodotoxin (1 μM), verapamil (10 μM), nifedipine (10 μM), ω-agatoxin IVA (200 nM), ω-conotoxin GVIA (1 μM), ω-conotoxin MVIIC (500 nM), or La 3+ (100 μM). These results suggest that palytoxin increases [Ca 2+] i in mouse spleen cells by stimulating Ca 2+ entry through an SKF-96365-, Ni 2+-sensitive pathway.
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