ADENOSINE STIMULATES HUMAN SPERM MOTILITY VIA A2 RECEPTORS

The effects of adenosine and its analogues on human sperm motility wer e studied using a transmembrane migration method. Specific binding sit es 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 increas es were both about 70%. 3,7-Dimethyl-1-propargylxanthine (DMPX), a pot ent A2 antagonist, competitively antagonized NECA-induced motility sti mulation. Successively higher concentrations of DMPX shifted the dose- response curve of NECA to the right in a nearly parallel fashion. Dipy ridamole, an inhibitor of adenosine uptake, does not reduce the abilit y of adenosine to stimulate human sperm motility. In radioligand-bindi ng studies, adenosine A1 selective analogues, cyclopentyl-1,3-dipropyl xanthine and 1-methyl-2-phenylethyl adenosine, have little competitive effect on [H-3]NECA binding in human sperm membrane. These results pr ovide evidence that adenosine enhances human sperm motility via adenos ine A2 receptors on the surface of sperm membranes.