Calcium requirement and increased association with bovine sperm during capacitation by heparin.
The requirement for external Ca+2 during capacitation of ejaculated bovine sperm with heparin and changes in sperm-associated 45Ca+2 during capacitation were investigated in vitro. Sperm capacitation was evaluated by ability to undergo an acrosome reaction (AR) upon exposure to lysophosphatidylcholine. The percentage of sperm which were capacitated during a 4 h incubation with heparin increased exponentially with increased exposure time to 2 mM Ca+2. When sperm were incubated with or without heparin in the presence of 45CaCl2, there was no difference in the amount of 45Ca+2 associated with sperm initially or at 1 h of incubation. Incubation with heparin resulted in a greater amount of sperm-associated 45Ca+2 at 2, 3, and 4 h as compared to sperm incubated without heparin. The amount of 45Ca+2 associated with sperm during capacitation was unaffected by washing with 2 mM EGTA-5 mM LaCl3. Glucose (5 mM) inhibited the effects of heparin on sperm-associated 45Ca+2 and on capacitation. The inhibitory effects of glucose could be overridden by 8-bromo-cAMP. The results suggest that the requirement for external Ca+2 during capacitation with heparin may be related to an increased association of external Ca+2 with sperm.
Handrow
R R
RR
Department of Meat and Animal Science, University of Wisconsin, Madison 53706.
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Parrish
J J
JJ
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D008297:Male; D013075:Sperm Capacitation / Q000502:physiology*; D013081:Sperm Motility; D013094:Spermatozoa / Q000378:metabolism*; D013997:Time Factors
D015124:8-Bromo Cyclic Adenosine Monophosphate; D006493:Heparin; D005947:Glucose; D002118:Calcium