Upregulation of pancreatic polypeptide-sensitive neuropeptide Y ( NPY) receptors in estrogen-induced hypertrophy of the anterior pituitary gland in the Fischer-344 rat.
Implants of diethylstilbestrol inducing anterior pituitary prolactinomas in female Fischer-344 rats produced a considerable elevation of high-affinity binding of either rat or human pancreatic polypeptide (hPP). No comparable upregulation of high-affinity binding sites was noted for the ligand [125I](Leu31,Pro34)hPYY (LP- PYY) (masked by 2 nM hPP to force selectivity for the Y1 sites), or of the Y2-selective ligand [125I]hPYY(3-36). The Y5-like sites displayed the rank order of potency of hPP = rPP, hNPY, LP- PYY > pPYY(1-36) > hNPY(2-36) > hPYY(3-36) >> aPP, similar to the previously described rabbit kidney or hypothalamic Y5-like receptors. The PP binding in the anterior pituitary was not sensitive to the Y1-selective non-peptidic antagonist BIBP-3226. The PP binding was highly sensitive to alkali metal cations, and to a N5-substituted amiloride antagonist of sodium transport, but not to a C2-guanido substituted amiloride antagonist of sodium channels. The binding was also sensitive to phospholipase C antagonist U-73122, and to alkylating alpha-adrenergic agonist chloroethylclonidine. Lactotrophs isolated in Percoll gradients after enzymic dispersion of the anterior pituitary gland retained the high-affinity PP binding. Following removal of estrogen implants, the hPP binding sites decreased to very low levels within 3 days, in parallel to the decrease of plasma prolactin.[1]References
- Upregulation of pancreatic polypeptide-sensitive neuropeptide Y (NPY) receptors in estrogen-induced hypertrophy of the anterior pituitary gland in the Fischer-344 rat. Parker, M.S., Wang, J.J., Fournier, A., Parker, S.L. Mol. Cell. Endocrinol. (2000) [Pubmed]
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