Aim: 

This is a preliminary study where we have investigated the intracellular calcium signal evoked by progesterone in ejaculated spermatozoa from men with normospermia or asthenozoospermia (low sperm motility).

Methods: 

Human semen was obtained from healthy volunteers by masturbation after 4-5 days of abstinence. Asthenospermia was characterised by reduced forward motility (WHO grade A+B sperm motility <50%) or absent sperm motility in fresh ejaculate. For [Ca²⁺]_c determination, the spermatozoa were loaded with the fluorescent ratiometric calcium indicator Fura-2 AM (4 mM, 30 min, room temperature).

Results: 

Our results show that the treatment of spermatozoa from normospermic men with 20 mM progesterone plus 1 mM thapsigargin in a calcium free medium induced a typical transient increase in [Ca²⁺]_c due to calcium release from internal stores. The subsequent addition of calcium to the external medium evoked a sustained elevation in [Ca²⁺]_c indicative of capacitative calcium entry. However, when progesterone plus thapsigargin were administrated to spermatozoa from patients with asthenozoospermia, the calcium signal was invaluable and the subsequent calcium entry was much smaller compared to normospermic patients. The treatment of spermatozoa with the cytoskeletal disrupter cytochalasin D (10 mM) or 10 mM jasplakinolide decreased the calcium entry evoked by depletion of internal calcium stores in normospermic patients, whereas these treatments proved to be ineffective to modify the calcium entry in patients with asthenozoospermia.

Conclusion: 

Our results suggest that spermatozoa from asthenozoospermic patients present abnormal calcium signalling.

Supported by Merck Farma y Química, S.L. (Merck-Serono). J. Espino was supported by Fundación Salud 2000 grant.