Identification of functional [alpha]2- and [beta]-adrenergic receptors in mammalian spermatozoa

• Published in: Human reproduction (Oxford) 2006-06, Vol.21 (6), p.1555
• Main Authors: Adeoya-Osiguwa, Susan A, Gibbons, Rachel, Fraser, Lynn R
• Format: Article
• Language: English
• ISSN: 0268-1161; 1460-2350

BACKGROUND: A recent study of several compounds, structurally related to amphetamine, provided evidence that mammalian spermatozoa might have adrenergic receptors able to regulate cAMP production. The present study investigated this possibility using physiological and immunochemical analyses of mouse and human spermatozoa. METHODS: Antibodies specific for different receptor subtypes were used for Western blotting of mouse and human sperm lysates and for immunocytochemical evaluation of whole mouse and human spermatozoa. Uncapacitated and capacitated mouse spermatozoa were incubated with specific agonists and antagonists for α2-, β1-, β2- and β3-adrenergic receptors for ∼35 min and then assessed using chlortetracycline (CTC) fluorescence. RESULTS: Western blotting revealed proteins of the correct size for all these receptors; immunolocalization indicated their presence on the head, especially acrosomal and neck regions, and flagellum of both mouse and human spermatozoa. CTC results indicated significant responses to agonists for all of the β-receptors in uncapacitated cells, with agonist effectiveness being β1 > β2 > β3; relevant antagonists blocked responses. In contrast, an agonist and antagonist for α2-receptors acted only on capacitated spermatozoa. CONCLUSION: These experiments provide the first good evidence that mammalian spermatozoa have both β-adrenergic receptors, known to stimulate cAMP production by membrane-associated adenylyl cyclases (mACs), and α2-adrenergic receptors, known to inhibit cAMP production by mACs. Responses are capacitation state dependent and provide a mechanism for inhibiting spontaneous acrosome reactions and helping to maintain fertilizing ability. These results suggest that the use of amphetamine-related compounds, either for medical or for social reasons, might have an unexpected positive impact on fertility.