Heparin-induced capacitation but not intracellular alkalinization of bovine sperm is inhibited by Rp-adenosine-3',5'-cyclic monophosphorothioate.
The objective of this study was to investigate the importance of cAMP during capacitation of bovine sperm. The competitive antagonist of cAMP, Rp-adenosine-3'5'-cyclic monophosphorothioate (Rp-cAMP), blocked heparin-induced capacitation (p < 0.05). The effect of Rp-cAMP on heparin-induced capacitation was reversed by 8-bromo-cAMP. The maximal inhibitory effect on capacitation occuroff when Rp-cAMP was added at the start of sperm incubation. These results support an important role for cAMP-dependent protein kinases during heparin-induced capacitation of bovine sperm. Further support for a role for protein phosphorylation during capacitation came from the use of the protein phosphatase inhibitor, okadaic acid. Okadaic acid had no affect on heparin-induced capacitation of bovine sperm (p > 0.05); however, bovine sperm were capacitated by okadaic acid in the absence of heparin (p < 0.05). The relationship of cAMP to capacitation-associated changes in sperm intracellular pH (pHi) was investigated using image analysis of bovine sperm. The pHi of sperm increased during capacitation, and Rp-cAMP did not affect the change in pHi. We conclude that heparin-induced capacitation of bovine sperm involves an increase in cAMP and a protein phosphorylation event but that these do not induce the increase in pHi associated with capacitation.
Department of Meat and Animal Science, University of Wisconsin, Madison 53706.
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Uguz
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Vredenburgh
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Parrish
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology; D004347:Drug Interactions; D004988:Ethers, Cyclic / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008297:Male; D019319:Okadaic Acid; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D013075:Sperm Capacitation / Q000187:drug effects* / Q000502:physiology; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology*
D004988:Ethers, Cyclic; D047428:Protein Kinase Inhibitors; D013873:Thionucleotides; D019319:Okadaic Acid; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016957:adenosine-3',5'-cyclic phosphorothioate; D006493:Heparin; D000242:Cyclic AMP