Dopamine in plasma of lateral and medial hypophysial portal vessels: evidence for regional variation in the release of hypothalamic dopamine into hypophysial portal blood

Details

Serval ID
serval:BIB_96593376C556
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Dopamine in plasma of lateral and medial hypophysial portal vessels: evidence for regional variation in the release of hypothalamic dopamine into hypophysial portal blood
Journal
Endocrinology
Author(s)
Reymond  M. J., Speciale  S. G., Porter  J. C.
ISSN
0013-7227
Publication state
Published
Issued date
06/1983
Peer-reviewed
Oui
Volume
112
Number
6
Pages
1958-63
Notes
Journal Article
Research Support, U.S. Gov't, P.H.S. --- Old month value: Jun
Abstract
The plasma concentrations of dopamine in blood from hypophysial portal vessels in various locations on the pituitary stalk were evaluated in diestrous rats. It was found that the mean concentration of dopamine in blood from lateral hypophysial portal vessels, which contain the venous effluent of the lateral median eminence, was significantly less (P less than 0.005) than that in blood from medial portal vessels, which contain the venous effluent of the medial median eminence [1.59 +/- (SE) 0.23 ng/ml vs. 3.12 +/- 0.48 ng/ml]. The mean plasma concentration of dopamine in blood of lateral portal vessels and of medial portal vessels was at least 20-40 times greater than that in arterial blood of these animals. It was calculated that the rate of release of hypothalamic dopamine was 174 +/- 38 pg/h into a medial portal vessel and 73 +/- 15 pg/h into a lateral portal vessel. The mean plasma concentration of norepinephrine or epinephrine in blood from a medial portal vessel was not different from that from a lateral portal vessel. To address the issue of whether the rate of release of dopamine into a medial portal vessel and into a lateral portal vessel was correlated with the rate of synthesis of dopamine in discrete regions of the median eminence, the concentration of L-dihydroxyphenylalanine (DOPA), the precursor of dopamine, was evaluated in lateral and medial segments of the median eminence of diestrous rats treated with 3-hydroxybenzylhydrazine, an inhibitor of DOPA decarboxylase activity. The concentration of DOPA was similar in the medial and lateral segments of the median eminence, suggesting that the rate of synthesis of dopamine did not account for the difference in the rate of release of dopamine into portal blood. The finding of different concentrations of dopamine in blood from various hypophysial portal vessels may be important in view of the heterogenous perfusion of the pars distalis with hypophysial portal blood. We suggest that topographic differences may exist in the release of PRL by cells of the pituitary gland as a consequence of uneven concentrations of dopamine in portal blood perfusing the lactotropes.
Keywords
Animals Dihydroxyphenylalanine/biosynthesis Dopamine/blood/*secretion Female Hypothalamo-Hypophyseal System/*blood supply Hypothalamus/*secretion Kinetics Organ Specificity Pituitary Gland/*secretion Rats
Pubmed
Web of science
Create date
11/02/2008 14:11
Last modification date
20/08/2019 14:58
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