Immunohistochemical Localization of Insulin‐Like Growth Factor‐I Receptor (IGF‐IR) in the Developing and Mature Rat Testes

Abstract

It has been suggested that insulin-like growth factor-I (IGF-I) plays an important role in the regulation of spermatogenesis in the testes. Its signal is mediated predominantly by the IGF-I receptor (IGF-IR). Signalling through IGF-IR has been shown to have a potent survival function. IGF-IR, a transmembrane tyrosine kinase, is widely expressed across many cell types. In this study, we demonstrated the distribution of IGF-IR in testes of differently aged rats. Anti-IGF-IR is a rabbit polyclonal antibody raised against a peptide mapping at the carboxy terminus of the IGF-IR of human origin. Testicular specimens were fixed in Bouin's solution and embedded in paraffin. The paraffin-embedded sections were processed for standard immunohistochemistry by the labelled streptavidin-biotin technique. At postnatal day 19, IGF-IR immunoreactivity was seen moderately in spermatogonia, and slightly both in leptotene and zygotene primary spermatocytes. At postnatal day 35, immunoreactivity was seen slightly both in the pachytene primary spermatocytes and Leydig cells. Although there was intense immunoreactivity in the Leydig cells and in the elongated spermatids on days 50 and 70, the intensity of reaction was decreased in the elongated spermatids in the 10th month. Our results suggest that IGF-IR may play significant roles in testicular function and germ cell development.

Localization of Insulin‐Like Growth Factor‐I (IGF‐I) and IGF‐I Receptor (IGF‐IR) in Equine Testes

“…In this present study, no IGF‐IR immunolabelling in Sertoli cells was observed at any age group, suggesting the IGF‐I system may not have a role in Sertoli cell function. A similar result showing the lack of IGF‐IR presence in Sertoli cells was previously reported in rats (Yagci and Zik 2006). In humans, the IGF‐IR immunolabelling of Sertoli cells was less intense than in Leydig cells (Vannelli et al.…”

“…The IGF‐IR labelling in Leydig cells was moderate in pubertal stallion, but became very strong in post‐pubertal stallions. The same pattern of IGF‐IR immunolabelling in the Leydig cells was reported in rats (Yagci and Zik 2006). This age‐dependent change in the immunolabelling appears to be because of the age‐associated modification in composition of Leydig cells.…”

“…The similar labelling suggests the presence of a paracrine/autocrine system important in supporting spermatogenesis. Immunohistochemical localization of IGF‐IR on germ cells was also observed in the developing and mature rat; the intensity of the labelling varied depending on types of germ cells and age of rats (Yagci and Zik 2006).…”

“…IGF‐I and IGF‐IR are localized in testicular cells in rats (Oonk and Grootegoed 1988; Hansson et al. 1989; Yagci and Zik 2006), pigs (Morera et al. 1987; Perrard‐Sapori et al.…”

“…1989). An immunohistochemical study in the developing and mature rat testes demonstrated the presence of IGF‐IR in spermatogonia and primary spermatocytes in immature rats (at post‐natal day 19), and in primary spermatocytes, elongated spermatids, and Leydig cells in mature rats (Yagci and Zik 2006). In human testes, strong immunolabelling of IGF‐IR was observed in secondary spermatocytes, early spermatids and Leydig cells, but less intense labelling was present in Sertoli cells (Vannelli et al.…”