| Monocrotaline (MCT) induced pneumotoxicity in rats is a model for pulmonary hypertension. To cause toxicity, MCT undergoes mandatory hepatic metabolism to yield a reactive metabolite monocrotaline pyrrole (MCTP) or dehydromonocrotaline. In the first study, we evaluated and compared effects of MCT, the MCTP metabolite, and its glutathione conjugate (GSH-DHP) on cultured bovine pulmonary endothelial cell monolayers (BPAECs). Pulmonary artery endothelial cells treated with MCTP (10 μg/ml) exhibited the classical signs of monocrotaline toxicity (megalocytosis, LDH release, altered prostacyclin function) while cells treated with MCT(60 μg/ml) and GSH-DHP (10 μg/ml) were not different from control cells treated with equivalent volume of vehicle (DMF).; My second study (Chapter 3) had two phases: one in vivo and the other in vitro. We performed ultrastructural studies to determine whether endothelial cells are specifically targeted by high dose MCTP (5 mg/kg) in vivo administered intravenously. Lung sections were examined with transmission electron microscopy at 4 hours and 24 hours post treatment. Widespread increase in paracellular space (interpreted as edema) at all levels of the pulmonary vascular tree was the most prominent lesion. In medium sized vessels, occasional swollen, necrotic cells were observed in situ. Scattered endothelial cells that appeared to be viable were observed to be partially detached from the underlying matrix in other medium sized vessels.; In the second part of Chapter 3, I compared three indicators of permeability: f-/g-actin ratios, gap size (area), and percent paracellular space to better define the mechanism of MCTP/thrombin interaction in bovine pulmonary artery endothelial cell monolayers and to determine whether this interaction affects states of polymerization of actin in those monolayers. I found that percent intercellular space was best correlated with measured permeability responses to MCTP and thrombin and the potentiation of dual treatment on endothelial monolayers reported in studies done by others in this laboratory.; Studies (presented in Chapter 4) in cultured monolayers were undertaken to look more closely at potential interactions of MCTP and thrombin on adhesion molecules involved in cell-cell and cell-matrix attachments and the potential for prolongation of the vascular leak observed very early in the process (Valdivia et al, 1967).; Treatment of endothelial cells with MCTP alone and in conjunction with thrombin revealed complexities involved in the interaction of a multifunctional moiety (MCTP) which has multiple pathways of inducing injury to endothelial cells. (Abstract shortened by UMI.)... |
