Objectives: The branching morphogensis of fetal mouse submandibular gland (SMG) is a basic developmental and cytodifferential process for forming the ducts and acini systems. Moreover, this process of branching morphogenesis is known to be dependent on reciprocal epithelio-mesenchymal interaction. And this process is stimulated by many growth factors, such as EGF or TGF-alpha. Steroid and thyroid hormones are also well known to induce the cytodifferention in the adult mouse SMG. We studied hormonal regulation of branching morphogenesis in the fetal mouse SMG in vitro. Methods: The fetal (the 13th day of gestation ,E13) SMG were organ cultured on Anocel filters in the culture chamber with 5alpha-dihydrotestosterone (DHT, 20 µ g/ml), triiodothyronine (T3, 2 µ g/ml) or dexametasone (Dex, 10 µ g/ml) in the BGJb medium at 0-72 hrs. And SMG rudiments were also incubated with EGF(2 ng/ml), FGF-10 (2 ng/ml) or IGF-1 (1 ng/ml) with or without anti-EGF, anti-FGF,or anti-IGF antibody (2 µ g/ml, respectively). Branching morphogenesiof organ cultuers were observed under photomicroscope, and EGF and IGF-1 content in the gland were measured by method of RIA and ELAISA. Expression of IGF-1 were observed by method of RT-PCR. Results: Branching morphogenesis of SMG was stimulated by injection of DHT and T3, but these branching process was reduced by Dex. Those inducing effects of DHT and T3 were inhibited by anti-FGF and anti-IGF but not to anti-EGF. The concentration of IGF-1 in the gland was increased by injection of DHT and T3. Moreover, the inhibitory effect of Dex disappeared by EGF. Conclusion: These results suggest that these hormones probably are involved in the regulation of IGF-1, but not EGF for this branching process, during fetal development and differentiation of mouse SMG.

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