Et. Donnelly et al., SPERM NITRIC-OXIDE AND MOTILITY - THE EFFECTS OF NITRIC-OXIDE SYNTHASE STIMULATION AND INHIBITION, Molecular human reproduction, 3(9), 1997, pp. 755-762
Nitric oxide (NO) is synthesized from L-arginine by a family of enzyme
s known as the nitric oxide synthases (NOS). We have recently shown a
NOS similar to constitutive brain NOS (bNOS) and endothelial NOS (ecNO
S) to be present in spermatozoa. The aim of this study is to investiga
te NO production by human spermatozoa and the effects of stimulation a
nd inhibition of NOS. This was carried out using the Iso-NO, an isolat
ed NO meter and sensor, which provides rapid, accurate and direct meas
urements of NO. Semen samples with normozoospermic and asthenozoosperm
ic profiles were prepared using a direct swim-up technique. Basal conc
entrations of NO and stimulated NO production were measured after expo
sure to the calcium ionophore (A23187; 0.01-10 mu M) a potent activato
r of constitutive NOS. NO production in human spermatozoa was signific
antly increased by the addition of A23187 30 seconds after stimulation
. Furthermore, this response was greatly diminished by pre-incubating
the samples with competitive inhibitors of L-arginine, the substrate f
or NOS, before treatment with calcium ionophore, in the presence of N-
G-nitro-L-arginine methyl ester (L-NAME), N-G-nitro-L-arginine (L-NA)
or N-G-methyt-L-arginine (L-NMMA; all at 10 mu M), NO production was i
nhibited with a rank order of potency L-NAME > L-NMMA > L-NA which is
in accordance with the inhibition of an endothelial type of constituti
ve NOS.