PAF binding sites. Characterization by [3H]52770 RP, a pyrrolo[1,2-c]thiazole derivative, in rabbit platelets |
| |
| Authors: | C Robaut G Durand C James D Lave P Sedivy A Floch S Mondot D Pacot I Cavero G Le Fur |
| |
| Institution: | 1. Rhône-Poulenc Santé, Centre de Recherches de Vitry, Departments of Biology, Vitry-sur-Seine Cédex, France;1. Chemistry, 13 Quai Jules Guesde, 94403 Vitry-sur-Seine Cédex, France;1. Catalysis and Peptide Research Unit, School of Health Sciences, University of KwaZulu-Natal, Durban, 4001, South Africa;2. HIV Pathogenesis Program, School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, Durban, 4001, South Africa;3. School of Chemistry and Physics, University of KwaZulu-Natal, Durban, 4001, South Africa;4. Faculty of Science and Agriculture, Department of Chemistry, University of Zululand, KwaDlangezwa, 3886, South Africa;1. School of Applied Sciences, Kalinga Institute of Industrial Technology (KIIT) Deemed to Be University, Bhubaneswar, 751024, India;2. Department of Chemistry, National Institute of Technology, Raipur, 492010, India;1. Department of Biotechnology, M S Ramaiah Institute of Technology, Bengaluru, 560054, Karnataka, India;2. Department of Biotechnology, Siddaganga Institute of Technology, Tumakuru, 572103, Karnataka, India;1. Institute of Nano Electronic Engineering, Universiti Malaysia Perlis (UniMAP), 01000, Kangar, Perlis, Malaysia;2. Faculty of Chemical Engineering Technology, Universiti Malaysia Perlis (UniMAP), 02600, Arau, Perlis, Malaysia;3. Centre for Chemical Biology (CCB), Universiti Sains Malaysia, Bayan Lepas, 11900, Penang, Malaysia;4. Faculty of Electronic Engineering Technology, Universiti Malaysia Perlis (UniMAP), 02600, Arau, Perlis, Malaysia;5. School of Biological Sciences, Universiti Sains Malaysia, Georgetown, 11800, Penang, Malaysia |
| |
| Abstract: | 52770 RP, the N-(3-chlorophenyl)-3-(3-pyridinyl)-1H,3H-pyrrolo1,2-c]thiazole -7-carboxamide, displaces in a potent, specific and competitive manner 3H]PAF from its binding sites on rabbit platelets. Since 52770 RP is not structurally related to PAF and has low liposolubility with respect to PAF, it was selected as a potential radioligand for PAF receptor sites. 3H]52770 RP displayed high-affinity, specificity, as well as saturable and displaceable binding to a single class of recognition sites in intact platelets and crude platelet membranes. In these preparations, the values of binding parameters were, respectively, 8.5 and 7.6 nM for Kd, 0.2 pmol/5 X 10(7) platelets and 3.66 pmol/mg protein for Bmax and 0.96 and 0.91 for nH. Inasmuch as the (+)-52770 RP was 300-fold more potent than the (-)-isomer at displacing 3H]52770 RP in intact platelets, the studied binding site manifested stereospecific discrimination. A variety of pharmacological agents including pro- and anti-aggregant compounds did not exhibit affinity for 3H]52770 RP binding sites. In contrast, PAF, some of its active analogues and several recognized PAF antagonists (BN 52021, brotizolam, L-652,731, triazolam), displaced the 3H]52770 RP binding. Studies carried out using 3H]PAF demonstrated that 52770 RP was approximately 4- and 200-fold more potent than L-652,731 and BN 52021 respectively, as a PAF-receptor antagonist. In washed rabbit platelets, the rank order of potency (Ki) for several analogues of 52770 RP, to displace 3H]PAF from its binding sites, was highly correlated (r = 0.96) to their ability to antagonize 3H]52770 RP binding. In functional studies, 52770 RP antagonized not only the PAF-induced aggregation in washed rabbit platelets but also the hypotension evoked by PAF in the anesthetized rat. In this respect, it was 26 and 2 times more potent than L-652,731, respectively. In conclusion, 3H]52770 RP might represent a novel interesting tool for furthering our understanding of the role of PAF binding sites in pathophysiological processes. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
