Mouse fetal kidneys in serum-free organ culture: effects of epidermal growth factor and hydrocortisone.

1. The present study was undertaken to determine whether epidermal growth factor (EGF, 100 ng/ml) or hydrocortisone (HC, 10(-8)-10(-5) M) directly influence proliferation and differentiation of mouse fetal kidney maturing in serum-free organ culture. 2. Addition of EGF to the medium significantly stimulated DNA synthesis after 2 and 5 days of culture. Labelled nuclei were mainly localized in the mesenchymal tissue. Protein synthesis remained unchanged. Activities of three hydrolases, markers of brush border differentiation, were reduced. 3. Hydrocortisone (HC), at all concentrations used, significantly inhibited DNA synthesis. Labelled nuclei were distributed in various cell populations of both control and treated explants. Protein synthesis was stimulated by 10(-7) M after 5 days of culture. Hydrolase activities were slightly modified by HC treatment. 4. The present results indicate that EGF stimulates whereas HC decreases proliferation. Both factors have regulatory effects on brush border maturation. 5. Thus, this culture model is a valuable tool for the study of nephrogenesis.