Immunohistochemical localization of insulin-like growth factor I (IGF-I) in the rat epididymis.

The distribution of insulin-like growth factor I (IGF-I) was studied by immunohistochemistry during postnatal development of the rat epididymis. At 2 weeks the immunoreactivity was mainly located along the cytoplasmic apical border in both the caput and the cauda epididymidis. A slight immunolabeling was present in the myofibroblastic cells. Afterward, the epithelial immunoreactivity was minimal at 4 weeks and increased progressively after the 6th week, especially in the apical and subapical cytoplasmic compartments of the caput epididymidis. The labeling of the epithelial cells of the cauda epididymidis was restricted to the apical cytoplasmic area. Immunolabeling was also found in the myofibroblastic cells and was more intense after 6 weeks. The variations of the pattern of distribution support the hypothesis of a physiological role for IGF-I in the regulation of epididymal functions.