Immunohistochemical localisation of epidermal growth factor, transforming growth factor alpha and EGF receptor during organogenesis of the murine hypophysis in vivo.

In previous study of melanocyte-stimulating hormone (MSH) cell development in the proliferating pars intermedia, which is in close apposition to the presumptive pars nervosa, no direct cell-to-cell contact was found between the boundary neurohypophyseal pituicytes (PIC), adenohypophyseal precursor stem cells (PSC) and the related diencephalic mesenchymal cells. Here, we have used immunohistochemistry to examine cytokine expression in the development of the hypophysis during foetal stages II-IV. Light and confocal laser scanning microscopy indicated diffuse expression of both TGF alpha and EGF in the hypophysis at different foetal stages. While no findings indicative for temporary changes of TGF alpha and EGF patterns were found in the foetal hypophysis, a temporary increment of EGF molecules was distinct in the diencephalic mesenchyme at stages III and IV. On the other hand, light microscopy intensively immuno-localized EGFR in the adenohypophysis and neurohypophysis at different developmental stages. Immunoreactivity of EGFR in the cytoplasm and nucleus suggested active proliferative events in the PIC and PSC of stages II-IV mouse pituitaries.