Immunohistochemical Visualizations of Prolactin, Growth Hormone, and a Substance Resembling Placental Lactogen in thein Situand Ectopic Pituitary in the Hamster*

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Abstract
The effects of transplanting neonatal adenohypophyseal tissue into the hamster cheek pouch on the presence of intracellular materials related to PRL in the allografts were examined using immunohistochemistry. In situ pituitary and placental tissue were used as control. Cells with antirat PRL-reactive sites were scarce in the grafts, and radioimmunoassayable serum PRL was not detectable in hypophysectomized hosts with grafts. Antirat GH- and antihuman placental lactogen (hPL)-reactive sites were visualized in the grafts and in situ pituitary tissue. Intracellular material in hamster placental tissue was visualized with anti-hPL only. Results of various immunohistochemical procedures using in situ pituitary tissue and antirat GH and anti-hPL antisera indicated that 3 cell types could exist: a cell type visualized with only antirat GH, a cell type visualized with only anti-hPL and a cell type, the most frequently observed, visualized with both antisera. The physiological significance of this intracellular product, which resembles hPL and perhaps hamster PL immunologically, in hamster adenohypophyseal cells is unknown. The ectopic site for pituitary transplantation in the hamster may influence the cell types present in the grafts.