Characterization of the effects of clomiphene citrate on reproductive physiology in male rats of various ages.

Clomiphene citrate (clomiphene) inhibits reproduction in male rats; however, stimulatory effects have been reported at low doses. Male rats were implanted at 60 (adult), 35 (peripubertal) or 10 (prepubertal) days of age with pellets that delivered 0, 0.05, 0.5 or 5.0 mg clomiphene.kg-1.day-1 and were sacrificed after 7 or 14 days of treatment. Testis weight was unaffected by clomiphene in adult and peripubertal rats, but was reduced by all doses in prepubertal rats. Seminal vesicle and prostate gland weights were decreased to varying degrees by clomiphene in all animals, except seminal vesicle weight in peripubertal rats. Serum LH and testosterone were decreased by most doses in all age groups, whereas pituitary LH was decreased in prepubertal rats only. Pituitary GnRH and testicular LH receptor concentrations were reduced in all treated animals. Serum and pituitary FSH were decreased in pre- and peripubertal rats, whereas testicular FSH receptor concentrations were unaffected by treatment. In summary, 1) reproductive function was compromised by clomiphene and many responses were age-dependent, 2) reductions in gonadotropins suggest that clomiphene decreased their synthesis and/or release, and 3) decreased serum LH and testicular LH receptor concentrations were coupled to reduced testosterone secretion.