Endocrine Abstracts

Objective: Decline in the number of D2 receptor (D2R) is considered as the reason of resistance to dopamine agonists (DA). PP4R2 gene was observed up-regulated in prolactinoma patients according to our previous genechip study. In this study, we demonstrated that PP4C was crucial for D2R expression and PRL secretion in rat pituitary MMQ cells.

Methods: In this study, we used rat pituitary MMQ cells which could secrete abundant prolactin and express functional dopamine receptors. RNA interference on PP4C gene was carried out in rat pituitary MMQ cells. The pCDH vector was used as a PP4C overexpression system to assess the functional consequences of PP4C overexpression. Total RNA and proteins were extracted from rat pituitary MMQ cells after PP4C silencing or overexpression. Q-PCR method was used to detect the changes in D2R mRNA levels. And western blotting was used to detect the changes in D2R protein levels. Enzyme-linked immunosorbent assay (ELISA) was carried using ELISA kit for rat PRL.

Results: PP4C silencing increased D2R expression and decreased PRL secretion in rat pituitary MMQ cells. PP4C overexpression reduced D2R expression and enhanced PRL secretion in rat pituitary MMQ cells.

Conclusion: Our study indicates that PP4C restrains D2R expression and increases PRL secretion in rat MMQ cells. These findings suggest the potential role of PP4C in the pathogenesis of prolactinoma.