HUMAN SPERM CAPACITATION INDUCED BY BIOLOGICAL-FLUIDS AND PROGESTERONE, BUT NOT BY NADH OR NADPH, IS ASSOCIATED WITH THE PRODUCTION OF SUPEROXIDE ANION
E. Delamirande et al., HUMAN SPERM CAPACITATION INDUCED BY BIOLOGICAL-FLUIDS AND PROGESTERONE, BUT NOT BY NADH OR NADPH, IS ASSOCIATED WITH THE PRODUCTION OF SUPEROXIDE ANION, Journal of andrology, 19(2), 1998, pp. 215-225
Recent evidence indicated that human sperm capacitation is associated
with an increased production of superoxide anion (O-2(.-)). To further
study the role and importance of O-2(.-) in capacitation,we investiga
ted whether the O-2(.-) generation is a general feature of capacitatin
g spermatozoa, irrespective of the inducer used, and is correlated wit
h capacitation levels and increased tyrosine phosphorylation of two sp
erm proteins (p105/p81). We also studied the time courses of O-2(.-) p
roduction and action. Percoll-washed human spermatozoa were incubated
in Ham's F-10 medium, supplemented or not supplemented with various ca
pacitation inducers and in the presence or absence of superoxide dismu
tase (SOD). Sperm capacitation was measured by induction of the acroso
me reaction with lysophosphatidylcholine, O-2(.-) production was measu
red by chemiluminescence, and tyrosine phosphorylation was measured by
immunodetection after electrophoresis and western blotting of sperm p
roteins. Progesterone and ultrafiltrates of human fetal cord serum, fo
llicular fluid, and seminal plasma individually promoted sperm generat
ion of O-2(.-), tyrosine phosphorylation of p105/p81, and capacitation
. Fetal cord serum ultrafiltrate triggered a five-fold higher O-2(.-)
production than the other inducers (1,700 +/- 300 and 300 to 400 mV/10
s/8 x 10(6) cells, respectively), a phenomenon possibly associated wit
h the higher potency of this fluid to promote sperm hyperactivation. T
he production of O-2(.-) by spermatozoa was rapid and transient. SOD p
revented sperm capacitation triggered by the inducers mentioned above,
but only when SOD was added at the beginning of incubation, and not a
fter 30 minutes, indicating that the O-2(.-) initiates a chain of earl
y events leading to sperm capacitation. NADH and NADPH (5 mM) triggere
d sperm capacitation and phosphorylation of p105/p81, but these proces
ses were not prevented by SOD or catalase, nor were they associated wi
th an increased O-2(.-) production. Therefore, these cofactors appeare
d to act by mechanisms different from those used by the other inducers
studied. The sperm enzyme responsible for the O-2(.-) generation may
be very different from the NADPH oxidase of neutrophils.