A retrospective analysis of pathological changes of testicular tissue in normal adult rats

Rat testicular model is widely used in experiments on andrology, pharmacology and reproductive toxicology. Generally, normal adult rat is considered to have normal testes. However, whether normal adult rats appeared abnormal testes have not been evaluated. The objective of this study was to evaluate the incidence of abnormal testes in normal adult Sprague Dawley (SD) rats and pathological changes in testicular tissues. Six hundred and sixteen adult male SD rats used in previous studies as controls were retrospectively analysed. Testicular tissues were stained with haematoxylin–eosin for observation of pathology. Among 616 rats, 14 rats had pathological testes, and the incidence of abnormal testis was 2.3%. In the 14 rats with abnormal testes, 10 rats were microrchidia (71.4%) and four rats showed normal testicular size. Testicular abnormality included complete interruption of spermatogenesis, partial germ cell arrest, progressive hypospermatogenesis, seminiferous epithelia vacuolation and inflammatory status. Bilateral testicular tissues had similar pathological changes in abnormal testes. The findings in this study demonstrate that the normal adult rats have abnormal testes. We should pay attention to the possibility of abnormal testes when using normal adult male rats for establishing a testicular model.