Study on antifertility effect of a novel LHRH antagonist in male rats

The potential of a novel LHRH antagonist, TX54, to inhibit reproductive function in male rats was evaluated. After subcutaneous injection at a dosage of 200 micrograms/rat, once a week for 2 weeks, all the drug-treated male rats maintained mating behavior. But, only one out of seven female rats mated to treated males was pregnant with two fetuses. At the end of medication, sperm count and motility of caudal epididymal spermatozoa of the treated rats were reduced significantly (TX54 vs. control: 11.3 +/- 3.2 x 10(8)/mg epididymal plasma, 66.4 +/- 13.4% vs 18.4 +/- 2.4 x 10(8)/mg epididymal plasma, 83.0 +/- 2.7%). Suppression of serum testosterone by TX54 was not observed 48 h after drug injection and at the end of experiment. Morphological examination revealed that at the IX stage of seminiferous epithelium cycle, spermiation was impaired in TX54-treated rats. Less elongated spermatids were found in the lumen of seminiferous tubules of the treated rats. The size of Leydig cells decreased; psychosis and apoptosis features occurred.