PROBLEM: Nitric oxide (NO) has been known to have multifunctional roles bot
h in the male and female reproductive systems. We investigated the effects
of sodium nitroprusside (SNP)-dependent NO release on sperm cell function a
nd embryo development to elucidate the mechanisms of action of NO.
METHOD OF STUDY: Semen samples from 20 healthy men were processed by the sw
im-up method. Sperm motility, hyperactivation, and acrosome reaction were e
xamined following incubation with various concentrations of SNP. The concen
tration of 10 nM to 1 mM was used for sperm motility and hyperactivation me
asurement and 1 I-IM to 1 mM for examining the effect on acrosome reaction.
Embryo development to blastocyst stage was assessed using 100 nM to 1 mM o
f SNP added before transferring the mouse embryos into the culture medium.
Finally, to understand the mechanism of action of NO, changes in embryo dev
elopment were examined after zygotes were treated with various concentratio
ns ranging up to 1 mM of 8-bromo-cGMP, an analog of cGMP.
RESULTS: Both sperm motility and hyperactivation were significantly reduced
at 100 mu M and 1 mM concentrations of SNP after 6 hr of incubation. After
24 hr of incubation, they were greatly decreased with all, except the 10 n
M concentration of SNP. The percentage of acrosomal-reacted spermatozoa was
increased with the increasing concentration of SNP following incubation wi
th 10 mu M and 1 mM of SNP. Embryo development was arrested since the two-c
ell embryonic stage with all except the 100 nhl concentration of SNP, and i
nhibited by 200 mu M of SNP regardless of SNP treatment stage. However, emb
ryo development was not influenced by 8-bromo-cGMP.
CONCLUSIONS: We concluded that SNP-inhibited sperm cell function and embryo
development in a dose- and time-dependent manner, and the inhibitory effec
t on embryo development, may not be a stage-specific treatment mediated via
a cGMP-independent pathway. This result suggests that NO may be enough to
affect the fecundity potential in vivo.