Mm. Creech et al., Sperm motility enhancement by nitric oxide produced by the oocytes of fathead minnows, Pimephelas promelas, J ANDROLOGY, 19(6), 1998, pp. 667-674
The effects of nitric oxide (NO) on sperm motility were examined in the fat
head minnow, Pimephelas promelas, using computer-assisted sperm analysis (C
ASA). The observed effects underscore the dual nature of NO as both a low-c
oncentration regulatory agent and, at higher doses, a cytotoxic agent. At 1
x 10(-6) M concentration, NO donor sodium nitroprusside (SNP) enhanced spe
rm motility percentages and increased CASA velocity parameters curvilinear
velocity, straight-line velocity, and average path velocity, whereas 1 x 10
(-2) M concentration inhibited percent motility and decreased velocities. F
athead minnow ova-produced NO was subsequently trapped as a paramagnetic fe
rrous iron complex and detected by electron spin resonance spectroscopy. Th
e distinctive triplet spectrum, with a(N) = 12.5G and g(iso) = 2.04, was re
corded during a critical 5-minute period following laying. Nitric oxide syn
thase (NOS) was histochemically localized at the micropyle of mature unfert
ilized fathead eggs, and an inhibitor of NOS blocked histochemical staining
. CASA analysis of sperm motility in the presence of ova-produced NO over a
n 8-minute time course reveals an optimum motility enhancement at 4 minutes
that is similar to the effect of 1 x 10(-6) M SNP. This transient NO produ
ction by freshly laid ova and the localization of NOS near the site of sper
m entry, together with the motility-enhancing effect of 1 x 10(-6) M SNP on
sperm, indicates an active role for low-concentration NO in fertilization.