Identification of specific binding sites for leukotriene C4 in membranes from human lung |
| |
| Authors: | G E Rovati D Oliva L Sautebin G C Folco A F Welton S Nicosia |
| |
| Affiliation: | 1. Institute of Pharmacology and Pharmacognosy, I-20129, Milan, Italy;2. Department of Pharmacology II, Hoffman-La Roche, Nutley, NJ 07110, U.S.A.;1. Division of Pharmacology, Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa;2. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 1 Jan Smut Ave, Braamfontein, Johannesburg, 2017, South Africa;3. School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK;4. School of Chemistry and Physics, University of KwaZulu-Natal, King Edward Drive, Pietermaritzburg, Scottsville, 3209, South Africa;1. Albert Einstein College of Medicine, New York, NY, United States;2. Universidad Nacional de San Agustín de Arequipa, Arequipa, Peru;3. Grupo de Investigación en Inmunología (GII), Arequipa, Peru;4. Columbia Center for Translational Immunology, Department of Medicine, Columbia University Medical Center, New York, United States;1. School of Pharmaceutical Sciences, Siksha ‘O’ Anusandhan Deemed to be University, Bhubaneswar, Odisha, India;2. College of Pharmaceutical Sciences, Dayananda Sagar University, Kumaraswamy Layout, Bengaluru, Karnataka, India |
| |
| Abstract: | Leukotriene C4 (LTC4), one of the major components of the slow-reacting substance of anaphylaxis (SRS-A), is a potent constrictor of bronchial smooth muscle in many species including humans. Here we report the identification and characterization of specific binding sites for LTC4 in membranes from human lung parenchyma. At 4 degrees, 3H-LTC4 binding is specific, saturable (Bmax = 32-41 pmoles/mg prot.), rapid (equilibrium being attained within 15 min), reversible and of high affinity (Kd = 3.6-7 X 10(-8) M). The binding sites are sensitive to heat and probably possess a protein moiety, being inactivated upon trypsinization. CaCl2 affects both the association and the dissociation rate and dose-dependently enhances the binding of 3H-LTC4 at equilibrium; maximal enhancement (4-fold) occurred at 10(-2)M CaCl2. Unlabelled LTC4 is able to complete with 3H-LTC4 for its binding sites with an IC50 of 7.8 X 10(-8) M. The addition of 10(-2) M CaCl2 increases the potency of LTC4 in inhibiting the binding (2.2-fold); both the competition curves are monophasic, indicating the existence of a homogeneous class of binding sites. In the presence of CaCl2, LTD4, LTE4 and the SRS-A antagonist FPL 55712 can inhibit 3H-LTC4 specific binding, being, however, less potent than LTC4 (IC50 S = 2.2 X 10(-6), 2.4 X 10(-5) M, for LTD4, LTE4 and FPL 55712, respectively). FPL 55712 displayed a competitive mechanism; its affinity, however, was lower if absorption to glass was not prevented. The present studies indicate that specific binding sites for 3H-LTC4 exist in human lung parenchyma, and that a receptor-mediated process might be involved in the bronchoconstriction induced by LTC4. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
