| Autor: |
Macháty, Zoltán, Ramsoondar, Jagdeece J., Bonk, Aaron J., Prather, Randall S., Bondioli, Kenneth R. |
| Zdroj: |
Biology of Reproduction; October 2002, Vol. 67 Issue: 4 p1133-1139, 7p |
| Abstrakt: |
The presence of the Na+/Ca2+exchange mechanism was investigated in porcine oocytes. Immature and in vitro-matured oocytes were loaded with the Ca2+-sensitive fluorescent dye fura 2 and changes in the intracellular free Ca2+concentration ([Ca2+]i) were monitored after altering the Na+concentration gradient across the plasma membrane. Decreasing the extracellular Na+concentration induced an increase in [Ca2+]ipossibly by a Ca2+influx via the Na+/Ca2+exchanger. A similar Ca2+influx could also be triggered after increasing the intracellular Na+concentration by incubation in the presence of ouabain (0.4 mM), a Na+/K+-ATPase inhibitor. The increase in the [Ca2+]iwas due to Ca2+influx since it was abolished in the absence of extracellular Ca2+, and the increase was mediated by the Na+/Ca2+exchanger since it was blocked by the application of amiloride or bepridil, inhibitors of Na+/Ca2+exchange. Verapamil (50 μM) and pimozide (50 μM), inhibitors of L- and T-type voltage-gated Ca2+channels, respectively, could not block the Ca2+influx. The Ca2+entry via the Na+/Ca2+exchanger could not induce the release of cortical granules and did not stimulate the resumption of meiosis. This was unexpected because Ca2+is thought to be a universal trigger for activation. Using antibodies raised against the exchanger, it was demonstrated that the Na+/Ca2+exchanger was localized predominantly in the plasma membrane. Reverse transcription-polymerase chain reaction revealed that porcine oocytes contain a transcript that shows 98.1% homology to the NACA3 isoform of the porcine Na+/Ca2+exchanger. |
| Databáze: |
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