Sperm-induced calcium oscillations of human oocytes show distinct features in oocyte center and periphery
✍ Scribed by Dr. Jan Tesarik; Mario Sousa; Carmen Mendoza
- Book ID
- 102528980
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 493 KB
- Volume
- 41
- Category
- Article
- ISSN
- 1040-452X
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✦ Synopsis
Abstract
Temporal and spatial characteristics of explosive periodic increases (spikes) of intracellular free Ca^2+^ concentration ([Ca^2+^]i) induced by sperm in human oocytes (Ca^2+^ oscillations) were analyzed by confocal laser scanning microscopy and compared to Ca^2+^ oscillations induced in oocytes by the thiol reagent thimerosal. During the steady‐state period of sperm‐induced Ca^2+^ oscillations, each individual [Ca^2+^]i spike invariably began from a focus in oocyte periphery and spread throughout the entire peripheral region before propagating to the central ooplasm. This peripheral Ca^2+^ wave was immediately followed by an explosive [Ca^2+^]i increase in the central ooplasm. However, this central [Ca^2+^]i rise only peaked when [Ca^2+^]i in the peripheral ooplasm was already on the decline. Moreover, the peak [Ca^2+^]i values were always considerably higher in the oocyte center than in the periphery. In contrast, thimerosal‐induced Ca^2+^ oscillations did not show this particular form of propagation. These data show that sperm‐induced Ca^2+^ oscillations have a unique pattern of spatial dynamics and suggest that the bulk of Ca^2+^ mobilized during each spike is released from stores that have a relatively high threshold for Ca^2+^‐induced Ca^2+^ release (CICR). These stores are poorly developed, if not absent, in the oocyte cortex, and CICR from them is triggered by previous CICR from another type of store with a lower threshold that are preferentially located in the oocyte cortex and act as a detonator. © 1995 Wiley‐Liss, Inc.