TESTICULAR DEGENERATION AND SPERMATID RETENTION IN YOUNG MALE-RATS

The incidence of spontaneous testicular atrophy and its morphological changes in relation to stage-specific spermatogenesis were investigate d in young Crl:CD(R)/BR male rats at 10-12 wk of age used as controls for toxicity screening during 1983-1990. The incidence of testicular d egeneration was 2.5% (5/197) in control rats used for oral toxicity st udies and 9.4% (31/327) in rats used for inhalation studies. The epidi dymal tubules of rats with testicular degeneration had exfoliated germ cells and low sperm density. The high incidence of testicular degener ation observed in the control rats used in inhalation studies may be r elated to the stress associated with immobilization in the restrainer during nose-only exposure conditions. The severity of testicular degen eration in the inhalation studies was mostly minimal. In these minimal ly affected testes, mature spermatids (step 19) were retained within n ormal-appearing germinal epithelium at spermatogenic stages IX-XIV. Al so, eosinophilic globular bodies (EGBs) were formed with elongated or mature spermatids throughout all spermatogenic stages, but the general architecture of germinal epithelium was normal in appearance. By elec tron microscopy, EGBs were sequestered necrotic spermatids, and the ge rm cell degeneration was associated with cytoplasmic vacuolation of Se rtoli cells. In moderate testicular degeneration, markedly decreased m aturing spermatids (steps 15-19) and a slight depletion of round sperm atids were observed in stages I-VIII. In severe testicular degeneratio n, seminiferous tubules were lined with 1-2 layers of round spermatids and spermatocytes with giant cell formation. The round spermatids ser ved as a marker to identify spermatogenic stages (I-VIII) of the atrop hic tubules. Also, in severe testicular degeneration, tubules in sperm atogenic stages X-XIV had no elongated spermatids, and spermatocytes w ere exfoliated with occasional giant cell formation. Many seminiferous tubules were lined with only 1-2 layers of spermatocytes, and specifi c germ cell markers were not present.