Modulation of rat epididymal gamma-glutamyl transpeptidase by nonylphenols

1. gamma-Glutamyl-transpeptidase (gamma-GTP), present at low levels in the testis, seminal vesicle, prostate gland and epididymis in rat at 4 days of age, showed rapid developmental increases at the time of weaning. 2. Administration of nonylphenols (NP) to the neonatal male rat pup (from d ays 1 to 15) impaired the subsequent development of gamma-GTP in the epidid ymis but not in the testis, seminal vesicles or prostate gland. 3. Single injection of NP to weaned pups at similar to 22 days of age decre ased gamma-GTP in the epididymis but not in other male accessory sex organs . This effect was transient, dose-dependent and blocked by the oestrogen re ceptor-specific antagonist ICI 182,780. 4. Single injection of oestradiol to weaned rat at similar to 22 days of ag e also decreased gamma-GTP in the epididymis but not in the testis, prostat e gland or seminal vesicles. 5. In in vitro assays, NP did not inhibit epididymal gamma-GTP activity eve n at 100 mu M final concentration. Under similar conditions, acivicin, a sp ecific inhibitor for gamma-GTP, showed a dose-dependent inhibition of gamma -GTP activity. 6. It is suggested that NP impair gamma-GTP expression in the epididymis of developing male rat and act in part via the oestrogen receptor.