Reduced levels of intracellular calcium releasing in spermatozoa from asthenozoospermic patients.
BACKGROUND
Asthenozoospermia is one of the most common findings present in infertile males characterized by reduced or absent sperm motility, but its aetiology remains unknown in most cases. In addition, calcium is one of the most important ions regulating sperm motility. In this study we have investigated the progesterone-evoked intracellular calcium signal in ejaculated spermatozoa from men with normospermia or asthenozoospermia.


METHODS
Human ejaculates were obtained from healthy volunteers and asthenospermic men by masturbation after 4-5 days of abstinence. For determination of cytosolic free calcium concentration, spermatozoa were loaded with the fluorescent ratiometric calcium indicator Fura-2.


RESULTS
Treatment of spermatozoa from normospermic men with 20 micromolar progesterone plus 1 micromolar thapsigargin in a calcium free medium induced a typical transient increase in cytosolic free calcium concentration due to calcium release from internal stores. Similar results were obtained when spermatozoa were stimulated with progesterone alone. Subsequent addition of calcium to the external medium evoked a sustained elevation in cytosolic free calcium concentration indicative of capacitative calcium entry. However, when progesterone plus thapsigargin were administered to spermatozoa from patients with asthenozoospermia, calcium signal and subsequent calcium entry was much smaller compared to normospermic patients. As expected, pretreatment of normospermic spermatozoa with both the anti-progesterone receptor c262 antibody and with progesterone receptor antagonist RU-38486 decreased the calcium release induced by progesterone. Treatment of spermatozoa with cytochalasin D or jasplakinolide decreased the calcium entry evoked by depletion of internal calcium stores in normospermic patients, whereas these treatments proved to be ineffective at modifying the calcium entry in patients with asthenozoospermia.


CONCLUSIONS
Our results suggest that spermatozoa from asthenozoospermic patients present a reduced responsiveness to progesterone.
Espino
Javier
J
Department of Physiology, Faculty of Science, University of Extremadura, Badajoz, Spain. jespino@unex.es
Mediero
Matías
M
Lozano
Graciela M
GM
Bejarano
Ignacio
I
Ortiz
Agueda
A
García
Juan F
JF
Pariente
José A
JA
Rodríguez
Ana B
AB
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D053627:Asthenozoospermia / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D015638:Cytochalasin D / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D047630:Depsipeptides / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008297:Male; D011374:Progesterone / Q000494:pharmacology; D011372:Progestins / Q000494:pharmacology; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
D047630:Depsipeptides; D004791:Enzyme Inhibitors; D011372:Progestins; C057531:jasplakinolide; D015638:Cytochalasin D; D011374:Progesterone; D019284:Thapsigargin; D002118:Calcium