DOPA Accumulates in the Hypothalamic-Hypophysial Portal Vessels and Is Taken into the Anterior Pituitary of NSD-1015-Treated Rodents

Telford, Nancy; May, Patrick C.; Sinha, Y. N.; Porter, John C.; Finch, Caleb E.

doi:10.1159/000126149

Cited by 2 publications

(4 citation statements)

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“…In our study, the concentrations of L-Dopa tested in the experiments were 1 and 10 µM. These selected concentrations are comparable to the levels found in the plasma of portal vessels (12). To elucidate whether L-Dopa treatment alters the secretion of ACTH, we examined the effects of locally produced DA and AADC inhibition on basal and CRH-stimulated secretion of ACTH.…”

Section: Accepted Articlementioning

confidence: 98%

“…In fact, Telford et al have shown that the concentration of L-Dopa is higher in portal blood than in peripheral circulation. The authors conclude that the major source of L-Dopa in the anterior pituitary is the portal blood supply because L-Dopa was not detected in this lobe when the portal circulation was interrupted by separating the pituitary stalk (12). Based on reported concentrations in portal blood of DA (6 ng/ml in diestrus rats; (11)) and L-Dopa (40 ng/ml in female rats treated with NSD 1015; (12)), we could assume that the greatest contribution of DA would be from an endogenous (anterior pituitary) source.…”

Section: Accepted Articlementioning

confidence: 99%

“…Previous research described that in some physiological or experimental conditions the anterior pituitary expresses TH (13) and synthesizes DA (14). However, in other studies TH activity in the anterior pituitary was not detected (12,15). In fact, Schussler et al (1995) reported that TH primary transcript suffers alternative splicing in the anterior pituitary, suggesting that this gland produces TH proteins with no enzymatic activity (16).…”

Section: Introductionmentioning

confidence: 96%

“…These observations suggest a pathway for the delivery of L-Dopa towards the hypophyseal portal circulation. In fact, while it was reported in female rats that the portal plasma DA concentration is around 6 ng/ml (11), Telford et al (1992) have observed that the L-Dopa concentration is around 40 ng/ml in NSD 1015-treated animals (12). The synthesis of DA by anterior pituitary cells has long been in debate.…”

Section: Introductionmentioning

confidence: 99%

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

Orrillo

Dios

Asad

et al. 2020

J Neuroendocrinology

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Prolactin (PRL) is a hormone principally secreted by lactotrophs of the anterior pituitary gland. Although the synthesis and exocytosis of this hormone are mainly under the regulation of hypothalamic dopamine (DA), the possibility that the anterior pituitary synthesizes this catecholamine remains unclear. In this study, our aim was to determine if the anterior pituitary produces DA from the precursor L-Dopa. To this purpose, we studied the expression of aromatic L-amino acid decarboxylase (AADC) enzyme and the transporter VMAT2 in the anterior pituitary, AtT20 and GH3 cells by immunofluorescence and western blot. Moreover, we investigated the production of DA Accepted Article This article is protected by copyright. All rights reserved from L-Dopa and its release in vitro. Then, we explored the effects of L-Dopa in the secretion of PRL from anterior pituitary fragments. We observed that the anterior pituitary, AtT20 and GH3 cells express both AADC and VMAT2. 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 levels in incubation media and reduced PRL secretion. Likewise, the content of cellular DA increased after AtT20 cells were incubated with L-Dopa. In addition, L-Dopa reduced CRH-stimulated ACTH release from these cells after AADC activity was inhibited by NSD-1015. Moreover, DA formation from L-Dopa increased apoptosis and decreased proliferation. However, in the presence of NSD-1015, L-Dopa decreased apoptosis and increased proliferation rates. These results suggest that the anterior pituitary synthesizes DA from L-Dopa by AADC and this catecholamine can be released from this gland contributing to the control of PRL secretion. In addition, our results suggest that L-Dopa exerts direct actions independently from its metabolization to DA.

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Section: Accepted Articlementioning

confidence: 98%

Section: Accepted Articlementioning

confidence: 99%