Follicular fluid proteins stimulate nitric oxide (NO) synthesis in human sperm: a possible role for NO in acrosomal reaction.
Nitric oxide (NO) is a free radical involved in the regulation of several functions of the male genitourinary system. It is produced by neurons and the endothelium and epithelia of reproductive system; it mediates penile erection and regulates sperm motility, viability, and metabolism. Here we show that human spermatozoa exhibit a detectable NO synthase (NOS) activity, measured both as ability of the intact sperm and cell lysate to convert L-[3H]arginine into L-[3H]citrulline and as 24 h accumulation of extracellular nitrite in intact sperm suspensions. NOS activity (identified as an endothelial isoform) was inhibited by L-canavanine and N(G)-monomethyl-L-arginine, and nitrite accumulation was inhibited by the NO scavenger hemoglobin; both enzyme activity and nitrite production were increased by a 24 h incubation of spermatozoa with protein-enriched extracts of human follicular fluid (PFF); a significant increase of citrulline synthesis was observed only after a 4 h incubation with 40% PFF, a time period during which acrosomal reactivity was significantly increased. PFF-induced acrosomal reaction was inhibited by L-canavanine and hemoglobin, and the NO donors sodium nitroprusside (SNP), S-nitroso-N-acetyl-penicillamine (SNAP), and DETA NONOate were able to increase the percentage of reacted spermatozoa. Our results suggest that NO synthesized by human sperm may play a role in follicular fluid-induced acrosomal reaction.
Revelli
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Department of Obstetrical and Gynecological Sciences, S. Anna Hospital, University of Torino, Italy. ghigo@molinette.unito.it
Soldati
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G
Costamagna
C
C
Pellerey
O
O
Aldieri
E
E
Massobrio
M
M
Bosia
A
A
Ghigo
D
D
D020101:Acrosome Reaction / Q000502:physiology*; D001826:Body Fluids / Q000737:chemistry / Q000201:enzymology; D002172:Canavanine / Q000494:pharmacology; D002956:Citrulline / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D006080:Ovarian Follicle / Q000378:metabolism*; D013094:Spermatozoa / Q000187:drug effects / Q000201:enzymology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D002956:Citrulline; D009569:Nitric Oxide; D002172:Canavanine; D019001:Nitric Oxide Synthase