Defective function of a nongenomic progesterone receptor as a sole sperm anomaly in infertile patients.

OBJECTIVE

To compare the function of a novel nongenomic progesterone (P) receptor on the human sperm surface (mediating the P-induced acrosome reaction) in spermatozoa from fertile donors and from infertile patients. To examine the possible implication of defective P receptor function as an etiologic factor in unexplained male infertility.

DESIGN

Progesterone binding and P effects were assessed in sperm from infertile patients and compared with corresponding parameters for sperm from healthy donors.

SETTING

Private hospital, medical research center, and a university-based andrological laboratory.

PATIENTS, PARTICIPANTS: Sperm samples were from infertile patients (no pathology detected in their wives) attending our infertility clinic and from healthy sperm donors.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Progesterone binding sites were visualized with a fluorescein-labeled protein-P conjugate. Indo 1-AM (a fluorescent indicator of intracellular free Ca2+) was used to measure P-induced Ca2+ influx. Progesterone-induced acrosome reaction was monitored after acrosomal staining with Pisum sativum agglutinin.

RESULTS

Among 8 patient sperm samples with normal spermiogram values (of 53 examined), 5 showed a reduced percentage of P-binding spermatozoa and an abnormal response to the hormone in terms of Ca2+ influx and the acrosome reaction.

CONCLUSIONS

Defective function of a sperm surface P receptor is described in some cases of male infertility. The observed fluorescence microscopic patterns of hormone binding may be used to further investigate receptor activity in unexplained male infertility.