Adenosine Stimulates Human Sperm Motility via A₂ Receptors

Abstract— The effects of adenosine and its analogues on human sperm motility were studied using a transmembrane migration method. Specific binding sites for adenosine in human sperm were also investigated. Adenosine and 5′‐N‐ethylcarboxamidoadenosine (NECA) stimulated human sperm motility with similar efficacies and the maximal amplitudes of motility increases were both about 70%. 3,7‐Dimethyl‐1‐propargylxanthine (DMPX), a potent A₂ antagonist, competitively antagonized NECA‐induced motility stimulation. Successively higher concentrations of DMPX shifted the dose‐response curve of NECA to the right in a nearly parallel fashion. Dipyridamole, an inhibitor of adenosine uptake, does not reduce the ability of adenosine to stimulate human sperm motility. In radioligand‐binding studies, adenosine A₁ selective analogues, cyclopentyl‐1,3‐dipropylxanthine and 1‐methyl‐2‐phenylethyl adenosine, have little competitive effect on [³H]NECA binding in human sperm membrane. These results provide evidence that adenosine enhances human sperm motility via adenosine A₂ receptors on the surface of sperm membranes. 1993 Royal Pharmaceutical Society of Great Britain