ABSTRACT
The distribution of transforming growth factor-α (TGF-α) and epidermal growth factor (EGF) in developing mouse embryos of gestational age 8 to 15 days was immunohistochemically (ABC method) studied to investigate the differential expression of these growth factors. Paraffin embedded sections were immunostained with antibodies for TGF-α and EGF. Staining of TGF-α was observed in several organs derived from endoderm, mesoderm and ectoderm in 9-day-old mouse embryos, such as in the heart, optic pit, head mesenchyme, neural tube and primitive gut, and the staining became more intense in 10 to 15-day-old mouse embryos. The staining of EGF was seen in the heart and primitive gut derived from mesoderm and ectoderm respectively, in 9-day-old mouse embryos, but it was observed in other organs as well in 10 to 15-day-old embryos although the intensity was weaker. In the development of heart, immunoreactivity for TGF-α was more intense than EGF, which suggests more active involvement of TGF-α. In the lung, TGF-α staining was observed both in the bronchus and lung bud, whereas EGF staining was seen only the bronchus. In the nervous system, TGF-α was expressed more extensively and more intensively than EGF. In the developing skeletal system, TGF-α staining was stronger and the expression was observed at earlier stage compared with EGF. These results indicate that the activity of TGF-α is more potent than EGF in the development of mouse embryo in general, especially, in the development of mouse heart, nervous system, mesenchyme and skeletal system.