Anterior pituitary gland synthesises dopamine from l ‐3,4‐dihydroxyphenylalanine ( l ‐dopa)

ORRILLO, SANTIAGO JORDI; DE DIOS, NATALY; ASAD, ANTONELA SOFÍA; DE FINO, FERNANDA; IMSEN, MERCEDES; ROMERO, ANA CLARA; ZÁRATE, SANDRA; FERRARIS, JIMENA; PISERA, DANIEL

JOURNAL OF NEUROENDOCRINOLOGY.

WILEY-BLACKWELL PUBLISHING, INC

Año: 2020 vol. 32

0953-8194

Prolactin (PRL) is a hormone principally secreted by lactotrophs of the anterior pituitary gland. Although the synthesis and exocytosis of this hormone are mainlyunder the regulation of hypothalamic dopamine (DA), the possibility that the anterior pituitary synthesises this catecholamine remains unclear. The present studyaimed to determine if the anterior pituitary produces DA from the precursor l-3,4-dihydroxyphenylalanine (l-dopa). Accordingly, we investigated the expression ofaromatic l-amino acid decarboxylase (AADC) enzyme and the transporter vesicularmonoamine transporter 2 (VMAT2) in the anterior pituitary, AtT20 and GH3 cellsby immunofluorescence and western blotting. Moreover, we investigated the production of DA from l-dopa and its release in vitro. Then, we explored the effects ofl-dopa with respect to the secretion of PRL from anterior pituitary fragments. Weobserved that the anterior pituitary, AtT20 and GH3 cells express both AADC andVMAT2. Next, we detected an increase in DA content after anterior pituitary fragments were incubated with l-dopa. Also, the presence of l-dopa increased DA levelsin incubation media and reduced PRL secretion. Likewise, the content of cellular DAincreased after AtT20 cells were incubated with l-dopa. In addition, l-dopa reducedcorticotrophin-releasing hormone-stimulated adrenocorticotrophic hormone releasefrom these cells after AADC activity was inhibited by NSD-1015. Moreover, DA formation from l-dopa increased apoptosis and decreased proliferation. However, inthe presence of NSD-1015, l-dopa decreased apoptosis and increased proliferationrates. These results suggest that the anterior pituitary synthesises DA from l-dopaby AADC and this catecholamine can be released from this gland contributing to thecontrol of PRL secretion. In addition, our results suggest that l-dopa exerts direct actions independently from its metabolisation to DA.