The use of in vitro fertilization to detect reductions in the fertility of male rats exposed to 1,3-dinitrobenzene.
1,3-Dinitrobenzene (DNB) is an intermediate chemical in the manufacture of dyes and explosives and its toxic effects include specific damage to the Sertoli cells of the testis. This investigation determined the effect a toxic insult to Sertoli cells had on the functional capacity of developing germ cells as assessed by in vitro fertilization. Male rats were given a single, oral dose of 5, 15, or 25 mg DNB/kg. At selected times after treatment, spermatozoa recovered from the cauda epididymidis were tested for fertilizing capacity using in vitro fertilization techniques and the testicular response to DNB was determined by histological examination. Treatment with 15 and 25 mg DNB/kg resulted in substantial exfoliation of germ cells between 0.5 and 3.5 weeks after exposure and again after 4.5 weeks; seminiferous tubules which were not depleted showed signs of disrupted spermatogenesis. Reduced sperm fertilizing capacity in vitro was observed from 1.5 to 5 weeks and between 7.5 and 8.5 weeks after treatment with 15 and 25 mg DNB/kg. There were slight, but significant, reductions in fertility at 3, 5.5, 7.5, and 8.5 weeks after dosing with 5 mg DNB/kg. These data suggested that DNB did not affect all Sertoli cells equally, but acted in a stage-specific manner. Stages III, IV, XII, and XIV were most vulnerable to the toxicant. Germ cells associated with an affected Sertoli cell were usually sloughed off, resulting in lowered fertility at the time when these cells should have reached maturity in the epididymis. The extent of the testicular lesions and the loss of fertility were dose dependent. This investigation confirmed the use of in vitro fertilization to detect the effects of testicular toxicants.