Fertilization envelope formation induced by melittin in sea urchin eggs does not depend on Ca2+ signalling |
| |
Authors: | Tadashi Tojo Yasuyuki Kamata Akiko Fujiwara Ikuo Yasumasu |
| |
Affiliation: | Department of Biology, School of Education, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-50, Japan. |
| |
Abstract: | In sea urchin eggs, 10 μg/mL melittin was found to induce fertilization envelope formation without any increase in [Ca2+]i (the intracellular free Ca2+ level). On the other hand, 10 μmol/L Br-A23187 and 100 μg/mL SDS induced fertilization envelope formation associated with [Ca2+]i increase. If EGTA was injected into eggs to make an intracellular concentration of 2 mmol/L, [Ca2+]i became quite low and was not altered by melittin, or by Br-A23187 and SDS. In eggs containing EGTA, fertilization envelope formation was induced by melittin even in Ca2+-free artificial sea water, but not by Br-A23187 or SDS. Thus [Ca2+]i is essential for induction of a fertilization envelope in sea urchin eggs by Br-A23187 or SDS but not by melittin. Melittin probably activates some Ca2+-independent reaction downstream of Ca2+-dependent reactions in a sequential reaction system that finally results in fertilization envelope formation. |
| |
Keywords: | Ca2+-signalling exocytosis fertilization envelope sea urchin melittin |
|
|