Evidence of the Existence of Adenylyl Cyclase 10 (ADCY10) Ortholog Proteins in the Heads and Connecting Pieces of Boar Spermatozoa

The aim of this study is to provide evidence of the existence of the adenylyl cyclase 10 (ADCY-10) ortholog proteins in boar spermatozoa. Experiments with RT-PCR techniques, nucleotide sequence analyses and Northern blot analyses revealed that boar testes exclusively express approximately 5.1-kbp RNA, the nucleotide sequence of which is highly similar to that of human A DCY10. Database analyses with CDART suggested that pig ADCY10 ortholog proteins conserve two catalytic domains of adenylyl cyclase. Western blot techniques and indirect immunofluorescence with a specific antiserum to pig recombinant ADCY10 ortholog proteins showed that 48-kDa and 70-kDa truncated forms of pig ADCY10 ortholog proteins are localized in the equatorial segments and connecting pieces of boar ejaculated spermatozoa. Finally, cell imaging techniques with fluo-3/AM indicated that incubation with sodium bicarbonate (an ADCY10 activator) can initiate the calcium influx in the boar sperm heads that is controlled via the cyclic AMP signaling cascades. These results are consistent with the suggestion that functional ADCY10 ortholog proteins exist in the heads of boar spermatozoa. This is the first direct evidence of the existence of ADCY10 proteins in the heads of mammalian spermatozoa.