Characterization of Opioid Binding Sites in the Neural and Intermediate Lobe of the Rat Pituitary Gland by Quantitative Receptor Autoradiography

Clifton VL, Owens PC, Robinson PJ, Smith R. Identification and characterization of a corticotrophinreleasing hormone receptor in human placenta. Eur J Endocrinol 1995;133:591–7. ISSN 0804–4643 Corticotrophin-releasing hormone (CRH) causes vasodilatation in the human fetal–placental circulation and has paracrine actions in placental tissue, suggesting that CRH receptors may be present in the human placenta. We have now identified and characterized placental CRH binding sites and compared them to those described previously in human myometrium and rat pituitary. Radiolabelled ovine CRH binding to placental membranes was pH-, time-, temperature- and divalent cation-dependent and was reversible in the presence of 1 μmol/l unlabelled ovine CRH. Scatchard analysis of placentae delivered vaginally or by elective caesarean section revealed dissociation constants (Kd) of 214.5 ± 84 pmol/l (N = 8) and 45.4 ± 23.9 pmol/l (N = 9), respectively. The Kd for caesarean placental binding sites was similar to that of human myometrium (59.6 pmol/l, N = 3) and rat pituitary (82.5 pmol/l, N = 3) receptors. However, in vaginally delivered placentae the CRH binding sites had a much lower affinity (p < 0.05). The receptor densities (Bmax) of vaginally delivered and caesarean-delivered placentae were 28.6 ± 9.6 and 6.1 ± 2.8 fmol/mg, respectively (p < 0.05). Chemical cross-linking studies using disuccinimidyl suberate indicated that the molecular weight of the CRH receptor in the placenta and rat pituitary is 75 kD. We conclude that there is a high-affinity population of CRH binding sites in the human placenta that are physicochemically similar to pituitary and myometrial CRH receptors. The CRH receptor properties in the placenta change in response to labour, when CRH levels in maternal blood are highest, suggesting that placental CRH may regulate its receptor. R Smith, Endocrinology Unit, John Hunter Hospital, Locked Bag 1, Hunter Regional Mail Centre, Newcastle, NSW 2310, Australia

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The D-2 Dopamine Receptor in the Intermediate Lobe of the Rat Pituitary Gland

Dopamine Receptors - ACS Symposium Series ◽

10.1021/bk-1983-0224.ch002 ◽

1983 ◽

pp. 33-72 ◽

Cited By ~ 2

Author(s):

J. W. KEBABIAN ◽

M. BEAULIEU ◽

T. E. COTE ◽

R. L. ESKAY ◽

E. A. FREY ◽

...

Keyword(s):

Pituitary Gland ◽

Dopamine Receptor ◽

Intermediate Lobe ◽

Rat Pituitary

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Immunocytochemical demonstration of tissue-type plasminogen activator in endocrine cells of the rat pituitary gland.

The Journal of Cell Biology ◽

10.1083/jcb.101.1.305 ◽

1985 ◽

Vol 101 (1) ◽

pp. 305-311 ◽

Cited By ~ 40

Author(s):

P Kristensen ◽

L S Nielsen ◽

J Grøndahl-Hansen ◽

P B Andresen ◽

L I Larsson ◽

...

Keyword(s):

Growth Hormone ◽

Pituitary Gland ◽

Endocrine Cells ◽

Large Population ◽

Cell Types ◽

Anterior Lobe ◽

Tissue Type ◽

Intermediate Lobe ◽

Posterior Lobe ◽

Rat Pituitary

We immunocytochemically stained rat pituitary glands using antibodies against plasminogen activators of the tissue type (t-PA) and the urokinase type (u-PA). A large population of endocrine cells in the anterior lobe of the gland displayed intense cytoplasmic immunoreactivity with anti-t-PA. In some areas of the intermediate lobe we found a weak staining, and we observed weakly staining granular structures in the posterior lobe. Controls included absorption of the antibodies with highly purified t-PA. In addition, SDS PAGE followed by immunoblotting of pituitary gland extracts revealed only one band with an electrophoretic mobility similar to that of t-PA when stained with anti-t-PA IgG. No u-PA immunoreactivity was detected in the rat pituitary gland. Sequential staining experiments using antibodies against growth hormone and t-PA demonstrated that the t-PA-immunoreactive cells constitute a large subpopulation of the growth hormone-containing cells. These findings represent the first direct evidence for the presence of t-PA in cell types other than endothelial cells in the intact normal organism. In this article we discuss the implications of the results for a possible role of t-PA in the posttranslational processing of prohormones.

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Vasopressin-binding sites in the pig pituitary gland: competition by novel vasopressin antagonists suggests the existence of an unusual receptor subtype in the anterior lobe

Journal of Endocrinology ◽

10.1677/joe.0.1410383 ◽

1994 ◽

Vol 141 (3) ◽

pp. 383-391 ◽

Cited By ~ 18

Author(s):

Y Arsenijevic ◽

M Dubois-Dauphin ◽

E Tribollet ◽

M Manning ◽

W H Sawyer ◽

...

Keyword(s):

Pituitary Gland ◽

Rat Liver ◽

Arginine Vasopressin ◽

Binding Sites ◽

Anterior Lobe ◽

Receptor Subtype ◽

Lower Affinity ◽

Corticotrophin Releasing Factor ◽

Rat Pituitary ◽

Acth Release

Abstract Arginine vasopressin (AVP) acts in the pituitary gland, in synergy with corticotrophin-releasing factor, to induce ACTH release in response to stressful stimuli. Pituitary AVP receptors in the rat are coupled to phospholipase C, as are the so-called V1-type AVP receptors. The present study examined [3H]AVP binding in membranes prepared from the anterior lobe of the pituitary gland of the pig. [3H]AVP, alone or in competition with analogues, bound to sites in the pig anterior lobe which are pharmacologically similar to those described previously by others in the rat pituitary gland. For comparison, the same competition studies were performed on membrane preparations from the rat liver which contain the classic V1-type AVP receptor. Pituitary and liver AVP-binding sites were dissimilar; both cyclic and linear V1 antagonists had, in general, a much lower affinity for pituitary AVP-binding sites than for those in the liver. Thus, Phaa-d-Tyr(Et)-Phe-Gln-Asn-Lys-Pro-Arg-NH2 (Phaa=phenylacetyl) has a 2500-fold greater affinity for the latter (negative logarithm of inhibition constant (pKi)=9·64) than for the former (pKi=6·22). One linear antagonist, Pa-d-Tyr-Phe-Val-Asn-Arg-Pro-Arg-Arg-NH2 (Pa=propionyl) had about equal affinities for liver and pituitary membranes (pKi=6·39 and 6·53 respectively). Another compound, Phaa-d-Tyr-Phe-Val-Asn-Arg-Pro-Arg-Arg-NH2 had the highest affinity found to date for binding to AVP sites in the pituitary (pKi=7·43). These findings suggest some ideas for the design of more potent and/or selective AVP analogues acting in the pituitary gland. Journal of Endocrinology (1994) 141, 383–391

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