Embryonic myosin heavy chain and troponin T isoforms remain in the cremaster muscle of adult rat cryptorchidism induced with flutamide.

We examined the immunolocalization of isoforms of muscle proteins, myosin and troponin, in the cremaster muscle of the undescended testis (cryptorchidism). In cryptorchid rats induced by a nonsteroidal androgen antagonist, flutamide, the cremaster muscle contained embryonic myosin and embryonic/cardiac troponin T in both immunofluorescence microscopy and Western blotting using antibodies against myosin and troponin T specific for embryonic, cardiac and fast skeletal muscles. However, in muscles other than the cremaster muscle, i. e., the masseter, pectoral and abdominal muscles, embryonic isoforms of these proteins were undetectable by immunohistochemistry with these antibodies, even in the muscles from cryptorchid rats. Our results showing that high levels of embryonic isoforms of muscle proteins were specifically present in the cremaster muscle of cryptorchid rats induced by flutamide suggest that flutamide treatment of pregnant rats might affect genes controlling the development of the lumbar region of the fetus body resulting in the presence of embryonic protein isoforms in the cremaster muscles which are closely associated with undescended testes.