RESUMEN
In order to investigate the expression patterns of the transforming growth factor (TGF)beta isoforms in the internal ear, an immunohistochemical study of rat embryos was performed. Rat embryos were taken on the 13th, 15th, 17th, and 19th day after conception and their internal ears were immunohistochemically stained against TGF beta1, beta2, and beta3. As a result, the 13-day-old embryo showed a very weak positivity to TGF beta1. After the 15th day of pregnancy, no reactivity to TGF beta1 was defected. Immunoreactivity to TGF beta2 was observed from the 15th day of pregnancy throughout the rest of the period. The ampulla of the semicircular canal and the cochlear duct showed a notably strong immunohistochemical reaction. A strong reaction to TGF beta3 was observed on the 15th day of pregnancy. However, no positive reactions were observed thereafter. A strong immunoreactivity was observed especially on the apical cytoplasms, the surfaces of the epithelial cells, and basement membranes of the cochlear duct, as well as the semicircular canals of the developing internal ear of rat embryo.