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Endotoxin binding on capillary endothelium and myocyte plasma membranes in perfused rat heartDepartment of Physiology
Department of Physiology
Department of Biology
Department of Surgery
Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida, USA
Department of Physiology
Department of Microbiology and Immunology, The American University of Beirut, Beirut, Lebanon
This work uses a novel heart-perfusion technique to measure [3H]-lipopolysaccharide ([3H]-LPS) binding on capillary endothelium and myocyte cell membranes in Sprague-Dawley rats. Free or serum-containing Ringer-Lock buffer was infused at a rate of 1 ml/min and in the presence of 20 mM K+ and [ 3H]-LPS through an aortic cannula, and the effluent was collected through a catheter introduced into the right atrium cavity. The capillary endothelial lining was removed by CHAPS treatment to expose the cardiac myocyte surface. A physical model describing 1:1 binding stoichiometry of [3H]-LPS with its receptors is proposed and the mathematical equations derived allow for the calculation of binding constants (kn), reversal constants (k-n), dissociation constants (kd), and residency time constants (
Journal of Endotoxin Research, Vol. 4, No. 1,
45-51 (1997) |
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). The results showed that the presence of serum in the perfusate, slowed the binding of [3H]-LPS with the endothelial lining and myocytes, but increased the residency time by 3- and 50-fold, respectively. Hence, the endothelium and myofiber may contain LPS receptors that can bind more strongly with the ligand in association with sCD14-like and LBP-like molecules in rat serum. Thus it is postulated that the affinity of LPS to its receptor subtypes is not strictly and specifically dependent on the CD14 binding profile.