Nitro(w)-arginine methyl ester treatment delayed the onset of puberty in female rats.

It is well documented that nitric oxide (NO) stimulates LHRH, LH and GH release. Present experiments were carried out to analyse whether the blockade of NO generation can affect body growth and puberty onset in female rats. Prepubertal female rats were treated with L-nitro(w) arginine methyl ester (NAME), a blocker of nitric oxide synthase, from day 25 to first estrous (400 or 800 mg/L in drinking water). We measured body growth, age and body weight at vaginal opening and first estrous, and the ovarian and uteri weights and serum LH and FSH concentrations the day of first estrous. Females treated with NAME showed a normal body growth pattern and a delayed puberty. Serum LH concentrations were increased in groups treated with NAME. This stimulatory effect was also observed in 30 and 90 day-old females decapitated 60 min after NAME administration (40 mg/Kg i.p.). We conclude that blockade of NO generation delays puberty in female rats by mechanism(s) other than its effects on LH release.