A new rat line (TS inbred rats) showing uni- or bilateral ectopic scrota in about 70% of the males was established. Ectopic scrota were elongated pouches of the thin muscle layer under the suprainguinal body skin, in which hypoplastic testes and epididymides were seen. Genetic analysis revealed that the ectopic scrotum was controlled by multiple genes. Groups of 5 normal, uni- and bilaterally affected rats were killed at 25 weeks of age. Histologically, ectopic testes of uni- and bilaterally affected rats showed arrest of spermatogenesis at the primary spermatocyte stage. Contralateral testes of unilaterally affected rats were normally descended and showed normal spermatogenesis. No abnormality was seen in the urinary system. Plasma concentrations of FSH were significantly elevated in bilaterally affected rats but plasma concentrations of testosterone and LH were unchanged in uni- and bilaterally affected rats. Pituitary contents of LH and FSH were significantly elevated in bilaterally affected rats. The endocrinological status of TS inbred rats was therefore similar to that of experimentally induced cryptorchid rats.
Summary. Sperm retention cysts were observed in the efferent duct of TE inbred rats at 15 weeks of age. Spermatozoa agglutinated in the efferent duct with destruction of the epithelium. Testicular weight increased or decreased. Diameter of the seminiferous tubules was enlarged in testes that increased in weight and germinal cells degenerated in the atrophied testes. After 30 weeks of age, the tubules of the efferent duct were sometimes replaced by scars and testicular atrophy became more frequent. In 3 out of 5 normal rats united by parabiosis with TE males for 25\p=n-\27 days, cysts occurred in the efferent duct.
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