MICROVASCULAR RESEARCH 43, 20-45 (1992) Organ-Derived Microvessel Endothelial Cells Exhibit Differential Responsiveness to Thrombin and Other Growth Factors’ PAULA N. BELLONI,*” DARRELL H. CARNEY,? AND GARTH L. NICOLSON*,~ *Department of Tumor Biology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030; and TDepartment of Human Biological Chemistry and Genetics, The University of Texas Medical Branch, Galveston, Texas 77550 Received May 11, 1989 To investigate the relationship between endothelial cells and organ-associated vascular physiology, microvascular endothelial cells were isolated from murine brain, lung, and liver tissues. During culture, these endothelial cells maintained certain differentiated character- istics common to all endothelial cells, but also showed organ-specific characteristics, with distinct patterns of responsiveness to various growth factors. Microvascular endothelial cells from all organs responded to endothelial cell growth factor (ECGF), but lung (LE-1) and brain (MBE-12) endothelial cells showed different responsiveness to thrombin (lo-60 nM), combinations of thrombin and ECGF, or thrombin and extracellular matrix. Liver sinusoidal endothelial cells (HSE) were relatively unresponsive to thrombin, but were the most re- sponsive of the endothelial cells to EGF. Endothelial cells isolated from lung and brain, where fluxes in vascular permeability are observed following injury, showed dramatic mor- phological alterations in response to nanomolar concentrations of thrombin. These cells also exhibited the highest amount of ?-thrombin binding at these concentrations. Scatchard analysis of ‘ZSI-thrombin binding indicated that LE cells have the highest affinity for thrombin, followed by MBE, with HSE exhibiting significantly lower affinity. The binding of ?- thrombin to these cells was inhibited by the TR-9 monoclonal antibody directed against fibroblast high-affinity thrombin receptors involved in thrombin-stimulated mitogenesis. The results suggest that the differences in growth stimulation observed between organ-derived endothelial cells in response to thrombin, ECGF, and EGF may relate to differential expres- sion of receptors for these factors. These observations demonstrate yet another aspect of the functional heterogeneity of the microvascular endothelium. D 1992 Academic PWSS, IN. The vascular endothelium is essential in maintaining proper hemostasis, selective barrier and permeability properties of blood vessels, and in mediating responses to various physiological and pathological stimuli (Cotran, 1967; Manjo, 1965; Thorgierrson and Robertson, 1978). Properties common to endothelial cells, re- gardless of vessel size or tissue location, include: a nonthrombogenic luminal cell ’ This work was supported by NIH-NC1 Grant R35-CA44352 (OIG) and Institutional Grant P30- CA16672 to G. L. Nicolson and NIH Grant DK-25807 to D. H. Carney. ’ Present address: Somatix Therapy Corp., Alameda, CA 94501. ’ To whom correspondence and reprint requests should be addressed at The Department of Tumor Biology-Box 108, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas 77030. 20 0026-2862192 $3.00 Copyright 0 1992 by Academic Press, Inc. All rights of reproduction in any form reserved Printed in U.S.A.