Strontium promotes calcium oscillations in mouse meiotic oocytes and early embryos through InsP3 receptors, and requires activation of phospholipase and the synergistic action of InsP3.
BACKGROUND
Sr2+ is the most efficient agent for mouse oocyte activation and functions by inducing Ca2+ oscillations. However, its specific mechanism of action remains unknown. Here we investigated the specificity and possible mechanism of Sr2+-induced Ca2+ oscillations in mouse oocytes and early embryos.


METHODS
Ca2+ oscillations in oocytes and embryos were measured by ratiometric fluorescence imaging using fura-2AM. The role of phospholipase C (PLC) and inositol trisphosphate (InsP3) receptors in Sr2+-induced Ca2+ oscillations was examined by selective inhibitors.


RESULTS
Sr2+ can induce Ca2+ oscillations in both immature and mature oocytes, and in early embryos. A cell cycle stage-dependent phenomenon to Sr2+ stimulation was observed in 1-cell embryos. By using a low molecular weight heparin to antagonize the function of InsP3 receptors, we were able to show that InsP3 receptors are essential for Sr2+-induced Ca2+ oscillations. Treating metaphase II (MII) oocytes with the PLC inhibitor, U73122, abolished Sr2+-induced increases in Ca2+. This inhibitory effect of U73122 could be rescued by microinjection of InsP3, indicating that Sr2+-induced Ca2+ oscillations require the synergistic action of InsP3.


CONCLUSIONS
Sr2+-induced calcium oscillations in mouse oocytes and early embryos are mediated through InsP3 receptors, and require PLC activation and the synergistic action of InsP3.
Zhang
Di
D
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100080, China.
Pan
Lei
L
Yang
Ling-Hai
LH
He
Xiao-Ke
XK
Huang
Xiu-Ying
XY
Sun
Fang-Zhen
FZ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology; D004357:Drug Synergism; D004622:Embryo, Mammalian / Q000378:metabolism; D047108:Embryonic Development / Q000187:drug effects; D004789:Enzyme Activation; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D008540:Meiosis; D051379:Mice; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology; D010312:Parthenogenesis; D011760:Pyrrolidinones / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000502:physiology; D013094:Spermatozoa / Q000502:physiology; D013324:Strontium / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D015220:Calcium Channels; D004963:Estrenes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D011760:Pyrrolidinones; D018160:Receptors, Cytoplasmic and Nuclear; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D010738:Type C Phospholipases; D002118:Calcium; D013324:Strontium