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Characterization of High-Affinity Dopamine D2 Receptors and Modulation of Affinity States by Guanine Nucleotides in Cholate-Solubilized Bovine Striatal Preparations (1986)

Kazmi, Syed M. I. ; Ramwani, Jai ; Srivastava, Lalit K. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Journal of neurochemistry 47 (1986), S. 0

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ISSN: 1471-4159

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: Abstract 3,4-Dihydroxyphenylethylamine (dopamine) D2 receptors, solubilized from bovine striatal membranes using a cholic acid-NaCl combination, exhibited the typical pharmacological characteristics of both agonist and antagonist binding. The rank order potency of the agonists and antagonists to displace [3H]spiroperidol binding was the same as that observed with membrane-bound receptors. Computer-assisted analysis of the [3H]spiroperidol/agonist competition curves revealed the retention of high- and low-affinity states of the D2 receptor in the solubilized preparations and the proportions of receptor subpopulations in the two affinity states were similar to those reported in membrane. Guanine nucleotide almost completely converted the high-affinity sites to low-affinity sites for the agonists. The binding of the high-affinity agonist [3H]N-n-propylnor-apomorphine ([3H]NPA) was clearly demonstrated in the solubilized preparations for the first time. Addition of gua-nylyl-imidodiphosphate completely abolished the [3H]NPA binding. When the solubilized receptors were subjected to diethylaminoethyl-Sephacel chromatography, the dopaminergic binding sites eluted in two distinct peaks, showing six- to sevenfold purification of the receptors in the major peak. Binding studies performed on both peaks indicated that the receptor subpopulation present in the first peak may have a larger proportion of high-affinity binding sites than the second peak. The solubilized preparation also showed high-affinity binding of [35S]guanosine-5′-(γ-thio)triphos-phate, a result suggesting the presence of guanine nucleotide binding sites, which may interact with the solubilized D2 receptors. These data are consistent with the retention of the D2 receptor-guanine nucleotide regulatory protein complex in the solubilized preparations and should provide a suitable model system to study the receptor-effector interactions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00784.x

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Suppression of NFκB activation and NFκB-dependent gene expression by tepoxalin, a dual inhibitor of cyclooxygenase and 5-lipoxygenase (1995)

Kazmi, Syed M. I. ; Plante, Richard K. ; Visconti, Vito ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 57 (1995), S. 299-310

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ISSN: 0730-2312

Keywords: tepoxalin ; anti-inflammation ; immunosuppression ; NFκB ; DNA binding ; transactivation ; IκB ; PDTC ; quantitative PCR ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Tepoxalin, a dual inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5LO) with cytokine modifying activity, is also a potent inhibitor of the transcription factor, nuclear factor κB (NFκB). NFκB is a pleiotropic activator that is involved in the regulation of many genes whose products participate in immune or inflammatory responses. Tepoxalin inhibited in a dose related manner NFκB activation by PMA + ionomycin or H2O2 in Jurkat and HeLa cells. TNF-α-induced NFκB was also inhibited by tepoxalin in HeLa cells, while relatively less marked inhibition was observed in Jurkat cells. Activation of NFκB in several monocytic cell lines was also suppressed by tepoxalin. However AP-1 stimulation under the same conditions was not affected by tepoxalin. Other CO, LO inhibitors such as naproxen or zileuton did not inhibit NFκB activities. This inhibitory activity of tepoxalin was further illustrated by its suppression of NFκB regulated genes such as IL-6 in PMA stimulated human PBL and c-myc in IL-2 dependent T cell lines. Tepoxalin also blocked PMA + ionomycin-induced IκB degradation in a time-dependent fashion. The possible mechanism of tepoxalin in NFκB activation and its potential clinical application are discussed.

Additional Material: 9 Ill.