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| Content Provider | PubMed Central |
|---|---|
| Abstract | Periodic increases in intracellular free calcium occur upon fertilization of golden hamster eggs (Miyazaki et al. 1986. Dev. Biol. 118:259-267). To investigate the underlying mechanism, inositol 1,4,5- trisphosphate (IP3) and guanine nucleotides were microinjected into the egg while Ca2+ transients were monitored by aequorin luminescence and/or hyperpolarization in the membrane potential, which indicates the exact timing and spatial distribution of the Ca2+ rise. Injection of IP3 induced an immediate Ca2+ transient of 13-18 s in the entire egg. The critical concentration of IP3 was 80 nM in the injection pipette (2 nM in the egg, assuming uniform distribution); the effect was all-or- none. The Ca2+ rise occurred even in Ca-free external medium. Injection of 5 mM GTP or 0.33 mM guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) (calculated intracellular concentration, 200 or 12 microM, respectively) caused a similar Ca2+ transient with a delay of 160-200 s. More than 50 microM GTP gamma S produced recurring and attenuating Ca2+ transients in a local area of the cytoplasm, with an initial delay of 25-40 s and intervals of 45-60 s. In Ca-free medium the first one to two Ca2+ transients occurred but succeeding ones were absent. Preinjection of guanosine-5'-O-(2-thiodiphosphate) inhibited the occurrence of both GTP gamma S-induced and sperm-induced Ca2+ transients in a dose-dependent manner. Neither pertussis nor cholera toxins had effect. It was proposed that sperm-egg interaction activates a GTP-binding protein that stimulates production of IP3, causing the first one to two Ca releases from internal stores, and also stimulates a pathway for elevation of Ca2+ permeability in the plasma membrane, thereby sustaining the repeated Ca2+ releases. |
| Starting Page | 345 |
| File Format | |
| ISSN | 15408140 |
| e-ISSN | 15408140 |
| Journal | The Journal of Cell Biology |
| Issue Number | 2 |
| Volume Number | 106 |
| Language | English |
| Publisher | The Rockefeller University Press |
| Publisher Date | 1988-02-01 |
| Access Restriction | Open |
| Rights Holder | The Rockefeller University Press |
| Subject Keyword | Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Cell Biology Medicine |
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