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

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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 β-LH or FSH antisera. However, a few NT-IR cells did not stain for β-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 β-LH-IR were colocalized in part of the cell granules. Castration caused a progressive decrease of the NT-IR in the β-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 ganules of the gonadotrophs and a few thyrotrophs, indicating that NT could be released together with gonadotrophins and TSH. Moreover, since gonad-ectomy results in typical qualitative and quantitative changes of NT-IR gonadotrophs, the intervention of the pituitary NT in the regulation of the hypo-physogonadal axis is strongly suggested.

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