Association of Acute, High-dose Cadmium Exposure with Alterations in Vascular Endothelial Barrier Antigen Expression and Astrocyte Morphology in the Developing Rat Central Nervous System

Clinical and experimental studies have demonstrated the neurotoxic and behavioural effects of cadmium. However, the exact pathophysiological mechanism(s) of cadmium neurotoxicity on the human central nervous system (CNS) is not completely understood. A rat blood–brain barrier (BBB) endothelial marker, the endothelial barrier antigen (EBA), has been identified and we have shown previously that an anti-EBA IgG1 antibody exclusively recognizes barrier-competent microvessels in the rat CNS and peripheral nervous system (PNS). Endothelial cells of peripheral tissues or brain regions possessing fenestrated microvascular endothelia do not display immunoreactivity for EBA. Here, we describe the application of sequential indirect immunofluorescence with anti-EBA, and an antibody directed against glial fibrillary acidic protein (GFAP), to evaluate the immunoreactivity patterns and morphological alterations in BBB microvessels and astrocytes, following a single, high dose of cadmium in normal, term-delivered young rats. We detected a moderate reduction in immunoreactivity and number of microvessels labelled by the anti-EBA in the forebrain, cerebellum and midbrain in cadmium-exposed rats compared with normal controls. We observed weakly GFAP-reactive astrocytes displaying cell bodies with ill-defined borders and blurred cytoplasm within the white and grey matter of cadmium-exposed brains. The astrocyte nuclei were markedly enlarged, intensely hyperchromatic and exhibited chromatin condensation with nuclear fragmentation. This study indicates for the first time that EBA is involved in, and could serve as a potentially useful marker for studying, cadmium neurotoxicity in the rat model system.