Ontogeny of reactivity to endothelial cell markers during development of the embryonic and fetal rat lung

Abstract

The reactivity of endothelial cells to putative endothelial cell-specific markers varies with species,with vessel size and with the organ studied. To determine their value in studies of fetal rat lung, and whether organ immaturity would also influence reactivity, we studied endothelial cell immunoreactivity to antibodies against Factor VIIIIvon Willebrand factor (VIII/vWF), and binding reactivity to Bandeiraea (Griffonia) simplicifolia 1 lectin (BSL 1) during rat fetal lung development. Using an indirect immunofluorescent technique to detect Factor VIIYvon Willebrand factor (VIIUvWF), endothelial cells lining the aortic arches were identified as early as day 11 of gestation (term= 22 days), prior to lung development. Immunoreactivity to VIIIIvWF was subsequently localized to intrapulmonary endothelial cells and was not dependent on vessel size. In contrast, binding reactivity of FITC-conjugated BSL 1 was observed to both endothelial cells and to the basement membrane of developing airways, thus limiting its value as endothelial cell marker. During very early lung development solitary angioblasts could not be identified by reactivity to either VIIYvWF antibodies or to BSL 1, and neither marker appears to be of value for studies of early angiogenic events.