Follicular fluid proteins stimulate nitric oxide (NO) synthesis in human sperm: A possible role for NO in acrosomal reaction
✍ Scribed by Alberto Revelli; Gianni Soldati; Costanzo Costamagna; Ombretta Pellerey; Elisabetta Aldieri; Marco Massobrio; Amalia Bosia; Dario Ghigo
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 191 KB
- Volume
- 178
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
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-[ 3 H]arginine into L-[ 3 H]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.