Identification of Neurotensin-lmmunoreactive Cells in the Anterior Pituitary of Normal and Castrated Rats

Abstract

The localization of neurotensin (NT) has been studied in the rat pituitary by means of immunocytochemistry at the light- and electron-microscopic levels. Cells immunoreactive for NT (NT-IR) were observed in the anterior lobe of rats of both sexes. Following an elution-restaining procedure, it was found that most of these NT-IR cells correspond to cells also reacting to beta-LH or FSH antisera. However, a few NT-IR cells did not stain for beta-LH nor FSH, but for TSH. The subcellular localization of NT was studied at the electron-microscopic level by means of the immunogold procedure. The immunoreactivity was always localized over the secretory granules. By using two sizes of gold particles, it was shown that NT- and beta-LH-IR were colocalized in part of the cell granules. Castration caused a progressive decrease of the NT-IR in the beta-LH- or FSH-positive cells, while the number of NR-IR, TSH-IR cells increased. After 2 weeks, NT-IR was mainly observed in this latter cell type. The present work demonstrates that NT-IR is localized within the secretory granules of the gonadotrophs and a few thyrotrophs, indicating that NT could be released together with gonadotrophins and TSH. Moreover, since gonadectomy results in typical qualitative and quantitative changes of NT-IR gonadotrophs, the intervention of the pituitary NT in the regulation of the hypophysogonadal axis is strongly suggested.