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Differential Emergence of Cortical Granule Breakdown and Electrophysiological Responses during Meiotic Maturation of Toad Oocytes
Author(s) -
IWAO YASUHIRO
Publication year - 1982
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.1982.00467.x
Subject(s) - perivitelline space , cortical granule , oocyte , toad , oocyte activation , ionophore , biology , andrology , granule (geology) , electrophysiology , medicine , endocrinology , microbiology and biotechnology , calcium , neuroscience , embryo , zona pellucida , paleontology
Oocytes of the toad, Bufo bufo japonicus , at various stages of progesterone‐induced maturation were stimulated by pricking or treatment with Ca‐ionophore A23187. Upon pricking, oocytes 14 hr after hormone treatment (PHT) underwent sequential activation responses, such as development of an activation potential, cortical granule breakdown (CGBD), and formation of a perivitelline space (PVS), like those of mature oocytes (18 hr PHT). When oocytes were pricked at 14 hr PHT, it took about 10 min for the wave of CGBD to spread over all the oocyte surface, in contrast to the case with mature oocytes in which it took about 150 sec. The rate of spread of CGBD was significantly less in the vegetal hemisphere than in the animal hemisphere in both mature and immature oocytes. Treatment with A23187 (1 μM) for 5 min induced an activation potential, and PVS formation by the oocytes from 10 hr PHT, which was 3–4 hr earlier than the time when these responses could be induced by pricking. Oocytes at 8–9 hr PHT also showed CGBD in response to A23187, but without formation of an activation potential. Several patches of local PVS caused by the non‐propagating CGBD were observed in oocytes treated with the ionophore 5–7 hr PHT. When a high concentration (10 μM) of A23187 was employed, CGBD without PVS formation was induced even in oocytes at 0 hr PHT. These results indicate that the responsiveness to a Ca 2+ surge that is a prerequisite for both CGBD and genesis of an activation potential is acquired for the repective responses at different stages of oocyte maturation.