MONOCROTALINE PYRROLE INTERACTS WITH ACTIN AND INCREASES THROMBIN-MEDIATED PERMEABILITY IN PULMONARY-ARTERY ENDOTHELIAL-CELLS

One of the earliest morphologic changes evident in the monocrotaline ( MCT) model of pulmonary hypertension in rats is microvascular leak. Wh ether this represents a direct effect of MCT metabolites or is seconda ry to inflammatory and thrombotic changes remains uncertain. To determ ine whether MCT directly affects endothelial cell permeability barrier function, we characterized the interaction of the reactive pyrrole in termediate of MCT (MCTP) with endothelial cell actin and characterized its effects on thrombin-mediated signal transduction and monolayer pe rmeability, Bovine pulmonary endothelial cells (BPAEC) treated with MC TP had altered distribution of filamentous actin evident by fluorescen ce microscopy. Correlative Western blots and autoradiography of actin isolated from BPAEC treated with C-14-MCTP showed comigration of actin and MCTP-derived C-14. MCTP treatment did not alter cellular free Ca2 + concentrations nor did it interfere with thrombin-mediated intracell ular Ca2+ signal. Pretreatment with MCTP significantly augmented the t hrombin-mediated transudation of Evan's blue albumin in BPAEC monolaye rs apparently by increasing the size of intercellular gaps. We conclud e that MCTP directly interacts with actin to alter its polymerization state but does not significantly affect endothelial cell response to c ontractile stimulus, Our results suggest that MCTP may affect endothel ial cell barrier function through alterations in intracellular junctio ns, (C) 1998 Academic Press.