Effect of medium milieu on sperm penetration and pronuclear formation of bovine oocytes matured in vitro.
The purpose of the present study was to investigate the optimal concentration of osmolarity, calcium and bicarbonate for sperm penetration and formation of pronuclei (PN), and to investigate the time required for capacitation, penetration across the zona pellucida and formation of PN in bovine cumulus-free oocytes matured in vitro. Bovine follicular oocytes collected at slaughter were matured and fertilized in vitro. Bovine sperm penetrated the zona pellucida in medium containing 240 to 440 mOsm, whereas PN formation was observed in a narrow range of osmolarities, from 280 to 360 mOsm. Maximal penetration by spermatozoa and PN formation was obtained in the medium with 2.5 mM calcium. High rates of spermatozoa penetration were observed in the medium with 37 to 49 mM NaHCO3. However, PN were formed regardless of the concentration of NaHCO3. The times required for sperm capacitation and penetration through the zona pellucida were 260 and 50 min, respectively. The first development of PN was recorded at 120 min after sperm penetration. Therefore, our study suggests that fertilization ability of spermatozoa in vitro appears to be more stable in high concentrations of NaCI. Oocytes are more sensitive to osmotic stress than spermatozoa. Calcium is required for both sperm penetration and PN formation in cumulus-free oocytes, but bicarbonate may be needed mainly for the penetration of spermatozoa.
Kim
Byung-Ki
BK
Faculty of Natural Science, Department of Biology, University of Dong-Eui, Kaya-Dong, Pusan, South Korea. bkkim@hyomin.dongeui.ac.kr
Lee
Sang-Chan
SC
Lee
Kwang-Sun
KS
Lee
Bok-Kyu
BK
Han
Chang-Hee
CH
Kim
Jong-Heung
JH
Lee
Chae-Sik
CS
D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000502:physiology*; D002478:Cells, Cultured; D003470:Culture Media; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D008297:Male; D009865:Oocytes / Q000502:physiology* / Q000648:ultrastructure*; D009994:Osmolar Concentration; D013084:Sperm-Ovum Interactions
D003470:Culture Media