Intracellular calcium oscillations and activation in horse oocytes injected with stallion sperm extracts or spermatozoa.
In oocytes from all mammalian species studied to date, fertilization by a spermatozoon induces intracellular calcium ([Ca(2+)](i)) oscillations that are crucial for appropriate oocyte activation and embryonic development. Such patterns are species-specific and have not yet been elucidated in horses; it is also not known whether equine oocytes respond with transient [Ca(2+)](i) oscillations when fertilized or treated with parthenogenetic agents. Therefore, the aims of this study were: (i) to characterize the activity of equine sperm extracts microinjected into mouse oocytes; (ii) to ascertain in horse oocytes the [Ca(2+)](i)-releasing activity and activating capacity of equine sperm extracts corresponding to the activity present in a single stallion spermatozoon; and (iii) to determine whether equine oocytes respond with [Ca(2+)](i) transients and activation when fertilized using the intracytoplasmic sperm injection (ICSI) procedure. The results of this study indicate that equine sperm extracts are able to induce [Ca(2+)](i) oscillations, activation and embryo development in mouse oocytes. Furthermore, in horse oocytes, injection of sperm extracts induced persistent [Ca(2+)](i) oscillations that lasted for >60 min and initiated oocyte activation. Nevertheless, injection of a single stallion spermatozoon did not consistently initiate [Ca(2+)](i) oscillations in horse oocytes. It is concluded that stallion sperm extracts can efficiently induce [Ca(2+)](i) responses and parthenogenesis in horse oocytes, and can be used to elucidate the signalling mechanism of fertilization in horses. Conversely, the inconsistent [Ca(2+)](i) responses obtained with sperm injection in horse oocytes may explain, at least in part, the low developmental success obtained using ICSI in large animal species.
Bedford
S J
SJ
Department of Veterinary and Animal Sciences, Paige Laboratory, University of Massachusetts, Amherst, MA 01003-9286, USA.
Kurokawa
M
M
Hinrichs
K
K
Fissore
R A
RA
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002478:Cells, Cultured; D005260:Female; D006736:Horses / Q000378:metabolism*; D008297:Male; D051379:Mice; D008845:Microinjections; D009865:Oocytes / Q000378:metabolism*; D009866:Oogenesis; D010312:Parthenogenesis; D013045:Species Specificity; D020554:Sperm Injections, Intracytoplasmic; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism*
D002118:Calcium