Volume regulation of mature and immature spermatozoa in a primate model, and possible ion channels involved.
BACKGROUND
Human ejaculated sperm undergo volume regulation, and swollen cells fail to penetrate mucus. Study of an infertile mouse model indicates maturation of volume regulation mechanism in the epididymis.


METHODS
Sperm from the ejaculate and three regions of the epididymis of the cynomolgus monkey (Macaca fascicularis) were dispersed in BWW medium and changes in the cell volume and kinematics, and their responses to ion channel blockers, were monitored by flow cytometry and motion analysis.


RESULTS
Initially swollen cauda epididymidal spermatozoa regained their original volume within 20 min, but not in the presence of 0.25 mM quinine. Corpus epididymidal spermatozoa underwent such regulatory volume decrease (RVD) to a lesser extent, with a similar response to quinine. Caput sperm showed no swelling throughout incubation. The chloride channel inhibitor NPPB also caused swelling of cauda spermatozoa and both quinine and NPPB decreased the efficiency of forward progression. RVD of ejaculated spermatozoa was inhibited by the K+ channel blockers quinine and 4-aminopyridine (4-AP) but not by tetraethylammonium, Ba2+ or Gd3+, or the specific potassium channel blockers charybdotoxin, margatoxin, dendrotoxin, apamin, glybenclamide or clofilium. Quinine and 4-AP also altered ejaculated sperm kinematics as reported in human ejaculated spermatozoa.


CONCLUSIONS
Quinine- and 4-AP-sensitive (implying K+) and NPPB-sensitive (implying Cl-) channels are involved in RVD of primate sperm, which develop this volume regulatory ability in the epididymis.
Yeung
C H
CH
Institute of Reproductive Medicine of the University Clinic, Münster, Germany. yeung@uni-muenster.de
Barfield
J P
JP
Anapolski
M
M
Cooper
T G
TG
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D004542:Ejaculation; D004822:Epididymis / Q000166:cytology; D005905:Glyburide / Q000494:pharmacology; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D008252:Macaca fascicularis; D008297:Male; D009498:Neurotoxins / Q000494:pharmacology; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D012604:Scorpion Venoms; D013094:Spermatozoa / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology
D007473:Ion Channels; D009498:Neurotoxins; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds; D012604:Scorpion Venoms; D018999:Charybdotoxin; D001030:Apamin; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C077910:margatoxin; D019789:Tetraethylammonium; C022799:clofilium; D011803:Quinine; D015761:4-Aminopyridine; D005905:Glyburide