Ultrastructural localization of IGF-I in the rat kidney; an immunocytochemical study.

We have shown recently by light microscopy that insulin-like growth factor I (IGF-I) immunoreactivity is localized in cells in the collecting ducts and in the thin loop of Henle in the normal rat kidney. In the present study, we have investigated the ultrastructural localisation of IGF-I using preembedding immunocytochemistry. The light microscopical findings were confirmed at the electronmicroscopical level. In collecting ducts as well as in the thin limb of Henle's loop a focal expression of IGF-I immunoreactivity was evident, i.e. distinctly IGF-I positive cells were intermingled with cells lacking IGF-I immunoreactivity. IGF-I immunoreactivity was found to have a diffuse cytoplasmatic distribution in both cell types. No specific association to organelles was found.