Inhibitory Effect of Calmodulin Antagonists and Calcium Antagonists on Fertilization-Induced Cyanide-Insensitive Respiration in Sea Urchin Eggs |
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Authors: | EMI TSUCHIDA AKIKO FUJIWARA YUKIO FUJINO TAKARA YONAGA IKUO YASUMASU |
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Institution: | Department of Biology, School of Education, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo, 160, Japan. |
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Abstract: | During initial several minutes after fertilization, sea urchin eggs exhibited high rate of respiration which was only slightly inhibited by cyanide. This cyanide-insensitive respiration was inhibited by calcium antagonists, diltiazem and verapamil, and calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalensulfonamide hydrochloride (W-7), N-(6-aminohexyl)-1-naphthalenesulfonamide hydrochloride (W-5) and chlorpromazine, which were added within 1 min after insemination. The inhibitory effect of W-7 on cyanide-insensitive respiration was higher than that of W-5. Cyanide-sensitive respiration of fertilized eggs observed after this initial period was not inhibited by these compounds. Ca2+ influx in eggs just after fertilization was inhibited by calcium antagonists but was rather enhanced by calmodulin antagonists. Fertilization-induced stimulation of cyanide-insensitive respiration probably results from calmodulin-dependent reactions which are activated by Ca2+ influx. |
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