Peroxisome proliferator-activated receptor (PPAR)γ is highly expressed in normal human pituitary gland

Objective: Expression of peroxisome proliferator-activated receptor (PPAR)gamma in normal pituitary seems to be restricted to ACTH-secreting cells. The aim of the study was to evaluate the expression of PPAR gamma in normal human pituitary tissue and to study its localization in the pituitary secreting cells. Materials and methods: Normal pituitary tissue samples were obtained form 11 patients with non-secreting adenoma who underwent surgical excision of the tumor. Expression of PPAR gamma was evaluated by immunostaining and western blotting; localization of PPAR gamma in each pituitary secreting cell lineage was evaluated by double immunofluorescence using confocal microscopy. Pituitary non-functioning adenomas served as Controls. Results: PPAR gamma was highly expressed in all pituitary samples with a (mean +/- SD) 81 +/- 6.5% of stained cells; expression of PPAR gamma was confirmed by western blotting. Non-functioning pituitary adenomas had 74 +/- 11 % PPAR gamma positive cells. Expression of PPAR gamma was either in cytoplasm or nuclei. In addition, treatment of GH3 cells, with a PPAR gamma ligand was associated with traslocation of the receptor from cytoplasm into the nucleus. Double immunostaining revealed that every pituitary secreting cell (GH, TSH, LH, FSH, PRL and ACTH) had PPAR gamma expressed. Discussion: The present study demonstrated that PPAR gamma is highly expressed in every normal pituitary secreting cell lineage. It can translocate into the nucleus by ligand binding; however, its role in pituitary hormone regulation remains to be elucidated.