Developmental changes in the intracellular Ca2+ release mechanisms in porcine oocytes.
The presence of different intracellular Ca2+ release mechanisms in porcine oocytes and their involvement in mediating Ca2+ transients in different developmental stages were investigated. Metaphase II arrested oocytes showed an increase in intracellular Ca2+ concentration after injection of inositol 1,4,5-trisphosphate (InsP3), the InsP3 receptor agonist. Similar Ca2+ spikes could be detected after injection of ryanodine and cyclic ADP ribose, the ryanodine receptor agonists. The InsP3-induced Ca2+ release was inhibited by heparin, the InsP3 receptor antagonist, whereas procaine, the ryanodine receptor antagonist, blocked the Ca2+ transients generated by ryanodine and cyclic ADP ribose. In germinal vesicle-stage oocytes, intracellularly stored Ca2+ could also be mobilized by agonist treatment, though the effective concentration to generate the Ca2+ spikes was higher. After in vitro fertilization, repetitive Ca2+ transients were generated in oocytes starting 2.5-3 h after insemination. They ceased around the time of pronuclear formation when the oocytes entered first interphase. At this stage, the receptors were still capable of mediating Ca2+ release upon agonist treatment; in many cases these spikes were of longer duration, suggesting that in interphase it takes a longer time for the Ca2+ stores to resequester the mobilized Ca2+ from the cytosol. These results suggest that porcine oocytes possess both InsP3 and ryanodine Ca2+ channel receptors and that the properties of the Ca2+ release mechanisms change during oocyte development.
Macháty
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Department of Animal Sciences, University of Missouri-Columbia 65211, USA.
Funahashi
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Prather
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D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry; D036563:Cyclic ADP-Ribose; D005260:Female; D005307:Fertilization in Vitro; D016257:Fura-2; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D008297:Male; D008677:Metaphase; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000037:antagonists & inhibitors / Q000737:chemistry; D012433:Ryanodine / Q000494:pharmacology; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology; D013552:Swine
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D000246:Adenosine Diphosphate Ribose; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium; D016257:Fura-2