Alterations of Testicular Function in the Unilaterally Cryptorchid Rat

Mature male Sprague-Dawley rats were either rendered unilaterally cryptorchid or used as intact controls. At 7, 14, 21, and 28 days postsurgery, five animals from each group were sacrificed, blood samples were collected, and the cryptorchid, eutopic, and intact control testes were removed. The cryptorchid testes weights decreased markedly below the controls while the weights of the eutopic testes did not vary from those of the controls. The levels of serum LH, FSH, and testosterone (T) did not significantly differ between the two groups throughout the study. The testicular content of T, expressed as nanograms per testis, decreased in the cryptorchid testes below control values from 30.6 ± 3.3 ng at 7 days to 10.8 ± 0.3 ng at 28 days while the content of the eutopic testes increased above controls from 71.1 ± 6.0 ng at 7 days to 131.7 ± 9.8 ng at 28 days. The cytoplasmic estrogen receptor level (³H-E₂ bound/mg protein) of the cryptorchid testis increased threefold above control levels at 7 days and continued to rise to a sixfold increase above control levels at 28 days; the eutopic and control E₂R levels did not vary throughout the study. While these data demonstrate that the steroidogenic capacity of the cryptorchid testis was reduced, the increased E₂ binding capacity indicates that the viability of the Leydig cell population was not detrimentally altered during the experimental period. These data further suggest that as a result of unilateral cryptorchidism, a compensatory change occurred in the eutopic testis resulting in an increased steroidogenic capacity in vivo.