2002 年 35 巻 4 号 p. 281-286
To study the protein expression of sex hormone receptors in relation to failure of the testicular descent (cryptorchidism), cryptorchid rats were obtained with administrating flutamide, an androgen antagonist, to pregnant rats. Immunolocalization of the androgen receptor (AR) and estrogen receptors α (ER α) and β (ERβ) was examined in the gubernaculum and cremaster muscle in cryptorchid rats. Testicular descent was normally completed by 4 weeks of age in rats. In control rat fetuses, AR and ERβ were expressed at high levels in fetal gubernaculum but were downregulated after birth. ERα was undetectable in fetal gubernaculum, but its protein expression was upregulated after birth. Similar results were found in the cremaster muscle. These results suggest that expression of AR, ERα and ERβ is developmentally regulated in the gubernaculum and cremaster muscle during the period of testicular descent. In cryptorchid rats, however, remarkable levels of expression of ERα and ERβ were detected in the gubernaculum at 2 weeks after birth. These strong expressions of ERα and ERβ decreased to control levels at 4 weeks. Immunoexpression of AR in cryptorchid rats after birth was the same level as that of control rats. These results indicate that flutamide significantly affects the expression of ERs, but AR expression less intensely. It is assumed that sex hormone receptors have an important role during the period of testicular descent.
