Effects of low concentrations of nitric oxide on the zona pellucida binding ability of human spermatozoa.
OBJECTIVE
To investigate the direct effects of sodium nitroprusside, a nitric oxide donor, on the fertilizing ability of human spermatozoa in vitro.


METHODS
Prospective, controlled in vitro study.


METHODS
IVF Unit, Medical College Hospital.


METHODS
Women undergoing conventional IVF.


METHODS
Human spermatozoa samples were incubated with a nitric oxide donor and a nitric oxide quencher, carboxy-imidazolineoxyl N-oxides.


METHODS
The capacitation and the acrosome reaction rates were determined by chlortetracycline assay. Sperm zona pellucida binding and sperm penetration into oocytes were determined using the hemizona assay and the human aged zona-free oocyte sperm penetration assay.


RESULTS
High concentrations of sodium nitroprusside (10(-3) and 10(-5) M) inhibited sperm motility and viability. In contrast, low concentrations of sodium nitroprusside (10(-7) and 10(-8) M) did not affect motility and resulted in increased capacitation (47 +/- 6% at 10(-7) M, 42 +/- 6% at 10(-8) M, and 24 +/- 4% in controls, respectively, P < 0.01). A twofold increase in the hemizona index occurred compared to the matched control. However, low levels of sodium nitroprusside treatment did not affect the acrosome reaction and human zona-free oocyte sperm penetration rates.


CONCLUSIONS
Low concentrations of nitric oxide may have some physiologic role in fertilization through the enhancement of capacitation and zona pellucida binding but not by the induction of the acrosome reaction or the facilitation of penetration into oocytes.
Sengoku
K
K
Department of Obstetrics and Gynecology, Asahikawa Medical College, Japan.
Tamate
K
K
Yoshida
T
T
Takaoka
Y
Y
Miyamoto
T
T
Ishikawa
M
M
D000177:Acrosome / Q000502:physiology; D001565:Benzoates / Q000494:pharmacology; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D009599:Nitroprusside / Q000008:administration & dosage / Q000494:pharmacology; D013075:Sperm Capacitation; D013081:Sperm Motility / Q000187:drug effects; D013084:Sperm-Ovum Interactions / Q000187:drug effects*; D013094:Spermatozoa / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism*
D001565:Benzoates; D007093:Imidazoles; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009599:Nitroprusside; D009569:Nitric Oxide