The effects of several ion channel blockers and calmodulin antagonists on fertilization-induced acid release and 45Ca2+ uptake in sea urchin eggs |
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Authors: | M Komukai A Fujiwara Y Fujino I Yasumasu |
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Institution: | 1. Department of Biology, School of Education, Waseda University, 1-6-1, Nishiwaseda, Shinjuku-ku, Tokyo, 160, Japan;2. Department of Pharmacology, Teikyo University School of Medicine, 2-11-1, Kaga, Itabashi-ku, Tokyo, 173, Japan |
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Abstract: | The effects of calcium antagonists, diltiazem and verapamil, and calmodulin antagonists, chlorpromazine, N-(6-aminohexyl)-1-naphthalenesulfonamide hydrochloride (W-5) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), were tested on two responses of the sea urchin egg to insemination: (1) H+ release; (2) Ca2+ uptake. It was found that calcium antagonists inhibited both processes, while calmodulin antagonists only inhibited H+ release but not Ca2+ uptake. Verapamil and diltiazem were effective to inhibit H+ release when added to the egg suspension up to 120 sec and W-7 was effective around 150 sec after insemination. Calcium antagonists became ineffective earlier than W-7 in inhibiting H+ release. A calmodulin-dependent step may thus occur linking the Ca2+ uptake and H+ release. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an anion channel blocker, also inhibited both Ca2+ uptake and H+ release. This result suggests that an uptake of anion(s) occurs along with Ca2+ uptake. |
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