Changes in intracellular calcium concentration in bovine oocytes following penetration by spermatozoa.
The pattern of changes in intracellular calcium concentration ([Ca2+]i) in bovine oocytes after penetration by spermatozoa was determined. Dynamic video imaging, using Fura-2 as a probe for intracellular free calcium, showed that activation of oocytes by spermatozoa induced multiple transient increases in [Ca2+]i with a spike interval of 24.2 +/- 7.3 min, and that the early transient increases were propagated throughout the oocytes in the form of a wave. Calcium transients at fertilization are involved in the induction of cortical granule exocytosis and the resultant block to polyspermy. The hypothesis that the inhibition of Ca2+ release from inositol trisphosphate-sensitive stores would inhibit exocytosis and increase polyspermy was tested by injecting oocytes before fertilization with heparin, a potent inhibitor of inositol trisphosphate-activated Ca2+ release. There was no significant difference after fertilization in either [Ca2+]i spikes or in polyspermy rates between control and experimental groups injected with low molecular mass heparin up to a final cytoplasmic concentration of 400 mumol l-1. We conclude that inositol trisphosphate-independent Ca2+ stores may be mobilized during the fertilization of bovine oocytes.
Sun
F Z
FZ
Department of Development and Signalling, Babraham Institute, Cambridge, UK.
Bradshaw
J P
JP
Galli
C
C
Moor
R M
RM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D005260:Female; D016257:Fura-2; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D013084:Sperm-Ovum Interactions; D014741:Video Recording
D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium; D016257:Fura-2