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Title: Characterization of a dopamine receptor (DA sub 2K ) in the kidney inner medulla

Abstract

Dopamine (DA) produces a natriuretic/diuretic response in the kidney by mechanisms that are still not well understood. There is some indication that DA{sub 2} receptors may be involved in mediating the effects of DA, but little is known regarding the nature of this receptor in the kidney. Autoradiographic localization of ({sup 3}H)spiperone, a DA{sub 2} antagonist, indicated that high-density binding was restricted to inner medullary collecting ducts (IMCDs). ({sup 3}H)Spiperone binding was saturable, high affinity and high density. Functionally, DA stimulated prostaglandin E{sub 2} production by IMCD cells, an effect that could be blocked by the DA{sub 2} antagonist domperidone. These results indicate that the kidney inner medulla expresses a functional DA receptor that may represent a newly identified DA receptor subtype (here designated DA{sub 2K}). Moreover, these results suggest that the kidney inner medulla may be a significant site at which DA, either directly or indirectly, influences water and electrolyte excretion.

Authors:
; ;  [1]
  1. (City Univ. of New York, NY (United States))
Publication Date:
OSTI Identifier:
6095185
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (United States); Journal Volume: 88:8
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; KIDNEYS; AUTORADIOGRAPHY; RECEPTORS; BIOCHEMICAL REACTION KINETICS; DIURETICS; DOPAMINE; INHIBITION; IODINE 125; PROSTAGLANDINS; SPIPERONE; AMINES; AROMATICS; AUTONOMIC NERVOUS SYSTEM AGENTS; BETA DECAY RADIOISOTOPES; BODY; CARDIOTONICS; CARDIOVASCULAR AGENTS; DAYS LIVING RADIOISOTOPES; DRUGS; ELECTRON CAPTURE RADIOISOTOPES; HYDROXY COMPOUNDS; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE ISOTOPES; ISOTOPES; KINETICS; MEMBRANE PROTEINS; NEUROREGULATORS; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; ORGANS; PHENOLS; POLYPHENOLS; PROTEINS; RADIOISOTOPES; REACTION KINETICS; SYMPATHOMIMETICS; 550604* - Medicine- Unsealed Radionuclides in Therapy- (1980-)

Citation Formats

Huo, T., Ye, M.Q., and Healy, D.P. Characterization of a dopamine receptor (DA sub 2K ) in the kidney inner medulla. United States: N. p., 1991. Web. doi:10.1073/pnas.88.8.3170.
Huo, T., Ye, M.Q., & Healy, D.P. Characterization of a dopamine receptor (DA sub 2K ) in the kidney inner medulla. United States. doi:10.1073/pnas.88.8.3170.
Huo, T., Ye, M.Q., and Healy, D.P. 1991. "Characterization of a dopamine receptor (DA sub 2K ) in the kidney inner medulla". United States. doi:10.1073/pnas.88.8.3170.
@article{osti_6095185,
title = {Characterization of a dopamine receptor (DA sub 2K ) in the kidney inner medulla},
author = {Huo, T. and Ye, M.Q. and Healy, D.P.},
abstractNote = {Dopamine (DA) produces a natriuretic/diuretic response in the kidney by mechanisms that are still not well understood. There is some indication that DA{sub 2} receptors may be involved in mediating the effects of DA, but little is known regarding the nature of this receptor in the kidney. Autoradiographic localization of ({sup 3}H)spiperone, a DA{sub 2} antagonist, indicated that high-density binding was restricted to inner medullary collecting ducts (IMCDs). ({sup 3}H)Spiperone binding was saturable, high affinity and high density. Functionally, DA stimulated prostaglandin E{sub 2} production by IMCD cells, an effect that could be blocked by the DA{sub 2} antagonist domperidone. These results indicate that the kidney inner medulla expresses a functional DA receptor that may represent a newly identified DA receptor subtype (here designated DA{sub 2K}). Moreover, these results suggest that the kidney inner medulla may be a significant site at which DA, either directly or indirectly, influences water and electrolyte excretion.},
doi = {10.1073/pnas.88.8.3170},
journal = {Proceedings of the National Academy of Sciences of the United States of America; (United States)},
number = ,
volume = 88:8,
place = {United States},
year = 1991,
month = 4
}
  • Previous studies by the authors laboratory have indicated that inner medullary collecting ducts (IMCDs) express a novel dopamine (DA) receptor, designated DA2K, that is linked to stimulation of prostaglandin E2 production. This receptor has a distinct pharmacological profile and is similar in size, but not homologous to, the brain D2 receptor. Because the DA2-selective antagonist domperidone blocks DA-mediated stimulation of prostaglandin E2 production in IMCD cells, we utilized (3H)domperidone to study the binding characteristics of the DA2K receptor in IMCD cells. (3H)Domperidone binding was saturable and best fit to a single high density site (KD, 57.6 {plus minus} 10.5 nM;more » Bmax, 14.9 {plus minus} 2.7 pmol/mg protein). The specificity of (3H)domperidone binding in IMCD cells was verified by competition analysis with a variety of dopaminergic and nondopaminergic agents. Dopaminergic drugs were less potent competitors for (3H)domperidone binding in IMCD cells than previously reported for brain DA receptors, but the rank order was consistent with the labeling of a DA receptor (antagonists: domperidone greater than spiperone greater than haloperidol greater than Sch 23390 much greater than (-)-sulpiride; agonists: norapomorphine greater than fenoldopam much greater than dopamine = quinpirole), and was better correlated with the pharmacological profile for the brain D2 receptor than the brain D3 receptor. In addition, quinpirole, the most D3-selective ligand currently available, did not compete for (3H)domperidone binding in IMCD cells. These results add further support to the existence of a novel high density DA receptor, DA2K, expressed in IMCD cells.« less
  • Dopamine increases cyclic AMP production in crude membrane preparations of cockroach brain with plateaus in cyclic AMP production occurring between 1-10 ..mu..M and 10 mM. Maximal production of cyclic AMP is 2.25 fold greater than that of control values. Octopamine also increases cyclic AMP production with a Ka of 1.4 ..mu..M and maximal production 3.5 fold greater than that of control. 5-Hydroxytryptamine does not increase cyclic AMP production. The effects of octopamine and dopamine are fully additive. The vertebrate dopamine agonists ADTN and epinine stimulate the dopamine-sensitive adenylate cyclase (AC) with Ka values of 4.5 and 0.6 ..mu..M respectively andmore » with maximal effectiveness 1.7 fold greater than that of control. The selective D/sub 2/-dopamine agonist LY-171555 stimulates cyclic AMP production to a similar extent with a Ka of 50 ..mu..M. Other dopamine agonists have no stimulatory effects. With the exception of mianserin, /sup 3/H-piflutixol is displaced from brain membranes by dopamine antagonists with an order of potency similar to that observed for the inhibition of dopamine-sensitive AC. The results indicate that the octopamine- and dopamine-sensitive AC in cockroach brain can be distinguished pharmacologically and the dopamine receptors coupled to AC have pharmacological characteristics distinct from vertebrate D/sup 1/- and D/sup 2/-dopamine receptors. 33 references, 3 figures, 2 tables.« less
  • Epidepride, (S)-N-((1-ethyl-2-pyrrolidinyl)methyl)-5-iodo-2,3-dimethoxybenzamide, the iodine analogue of isoremoxipride (FLB 457), was found to be a very potent dopamine D2 receptor antagonist. Optimal in vitro binding required incubation at 25C for 4 h at pH 7.4 in a buffer containing 120 mM NaCl, 5 mM KCl, 2 mM CaCl{sub 2} and 1 nM MgCl{sub 2}. Scatchard analysis of in vitro binding to striatal, medical frontal cortical, hippocampal and cerebellar membranes revealed a K{sub D} of 24 pM in all regions, with Bmax's of 36.7, 1.04, 0.85, and 0.37 pmol/g tissue, respectively. The Hill coefficients ranged from 0.91-1.00 in all four regions. Themore » IC{sub 50}'s for inhibition of ({sup 125}I)epidepride binding to striatal, medial frontal cortical, and hippocampal membranes for SCH 23390, SKF 83566, serotonin, ketanserin, mianserin, naloxone, QNB, prasozin, clonidine, alprenolol, and norepinephrine ranged from 1 {mu}M to >10 {mu}M. Partial displacement of ({sup 125}I)epidepride by nanomolar concentrations of clonidine was noted in the frontal cortex and hippocampus, but not in the striatum. Scatchard analysis of epidepride binding to {alpha}{sub 2} noradrenergic receptors in the frontal cortex and hippocampus revealed an apparent K{sub D} of 9 nM. At an epidepride concentration equal to the K{sub D} for the D2 receptor, i.e., 25 pM, no striatal {alpha}{sub 2} binding was seen and only 7% of the specific epidepride binding in the cortex or hippocampus was due to binding at the {alpha}{sub 2} site. Correlation of inhibition of ({sup 3}H)spiperone and ({sup 125}I)epidepride binding to striatal membranes by a variety of D2 ligands revealed a correlation coefficient of 0.99, indicating that epidepride labels a D2 site.« less
  • Multiple D{sub 1} dopaminergic receptor subtypes have been postulated on the basis of pharmacological, biochemical, and genetic studies. The authors describe the isolation and characterization of a rat gene encoding a dopamine receptor that is structurally and functionally similar to the D{sub 1} dopamine receptor. The coding region, which is intronless, encodes a protein of 475 amino acids (M{sub r} 52,834) with structural features that are consistent with receptors coupled to guanine nucleotide-binding regulatory proteins. The expressed protein binds dopaminergic ligands and mediates stimulation of adenylyl cyclase with pharmacological properties similar to those of the D{sub 1} dopamine receptor. Themore » gene encoding the human homologue of this receptor subtype is located to the short arm of chromosome 4 (4p16.3), the same region as the Huntington disease gene. In striking contrast to the previously cloned D{sub 1} receptor, little or no mRNA for the receptor described here was observed in striatum, nucleus accumbens, olfactory tubercle, and frontal cortex. High levels of mRNA for this receptor were found in distinct layers of the hippocampus, the mammillary nuclei, and the anterior pretectal nuclei, brain regions that have been shown to exhibit little or no D{sub 1} dopamine receptor binding. On the basis of its properties the authors propose that this dopamine receptor subtype be called D{sub 1B}.« less
  • FIDA2, (R)-(+)-2,3-dimethoxy-5-iodo-N-[1-(4`-fluorobenzyl)-2-pyrrolidinyl)-methyl]benzamide, is a new dopamine D2/D3 receptor imaging agent that can be labeled with either I-123 or F-18 for SPECT or PET imaging. In vitro binding studies of I-125 FIDA2 using dopamine D2 or D3 receptors expressed in Sf9 cells showed Kd values of 0.04 and 0.05 nM, respectively. In rat striatal homogenates, which contain a high density of dopamine D2 receptors, the ligand displayed a Kd of 0.04-0.06 nM. A series of in vivo SPECT images (transaxial sections, 2 mm) showed the radioactivity was localized in the area of the basal ganglia and reached peak concentrations in 11.2more » {plus_minus} 5.9 min. The activity cleared at a rate of 33.5 {plus_minus} 9.4 %/hr. The target to nontarget ratios (basal ganglia to cerebellum) at time of peak, 1 hr, 2 hr and 3 hr p.i., were 1.1 {plus_minus} 0.4 (n=21), 3.5 {plus_minus} 1.0 (n=20), 6.3 {plus_minus} 2.9 (n=9, and 8.14 {plus_minus} 4.7 (n=9), respectively. At 90 min an injection of haloperidol or raclopride, dopamine D2/D3 receptor antagonists, displaced target activity but an injection of SCH23390, a dopamine D1 receptor antagonist, had little effect on activity in the basal ganglia. In addition, an injection of R-(+)-7-OH-PIPAT, a new ligand that is selective for the dopamine D3 receptor and the high affinity state of the dopamine D2 receptor, showed partial displacement ({approximately}15%) of I-123 FIDA2 binding in the basal ganglia. These studies indicate that FIDA2 may be a useful ligand for in vivo imaging of dopamine D2/D3 receptors.« less