Capacitation state-dependent changes in adenosine receptors and their regulation of adenylyl cyclase/cAMP.
This study was designed to localize adenosine receptors and to provide evidence that specific receptors are active only in either uncapacitated or capacitated mouse spermatozoa, where they play a role in regulating cAMP production. Using specific antibodies, stimulatory A(2A) receptors were localized primarily on the acrosomal cap region and the flagellar principal piece. Interestingly, the staining was much more pronounced in uncapacitated than in capacitated spermatozoa, suggesting capacitation-dependent changes in epitope accessibility. A(1) receptors showed a very similar distribution, but the staining was markedly greater in capacitated than in uncapacitated cells. After addition of purified decapacitation factor (DF) to capacitated cells, strong staining for A(2A) was regained, suggesting reversibility in epitope accessibility. Chlortetracycline analysis revealed that an agonist specific for A(2A) receptors had no detectable effect on capacitated cells, but after DF-induced decapacitation, the agonist then stimulated capacitation. That agonist also significantly stimulated cAMP production in uncapacitated cells, had no effect on capacitated cells, but regained the ability to stimulate cAMP in the latter following DF treatment. In contrast, an A(1) agonist inhibited cAMP in capacitated cells. These results indicate that specific adenosine receptors function in a reversible manner in one or other capacitation state, resulting in regulation of cAMP.
Endocrinology and Reproduction Research Group, School of Biomedical Sciences, King's College London, Guy's Campus, London Bridge, London, United Kingdom.
Susan A
SA
Adeoya-Osiguwa
Lynn R
LR
Fraser
D000177:Acrosome / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism; D008297:Male; D051379:Mice; D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology
D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1; C056426:CGS 24012; C048599:N(6)-cyclopentyladenosine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D000241:Adenosine