COEXPRESSION OF BETA-1-ADRENERGIC AND BETA-2-ADRENERGIC RECEPTORS ON BOVINE BRAIN CAPILLARY ENDOTHELIAL-CELLS IN CULTURE

The pharmacological study of the blood-brain barrier has often been hampered by the unavailability of a large number of pure and fully differentiated brain capillary endothelial cells. Here we describe a homogeneous culture of brain capillary endothelial cells isolated from bovine brain (BBECs), which retain at least some phenotypic characteristics of the functional blood-brain barrier: intercellular tight junctions and monoamine oxidase activity. These cells were subcultured in vitro, in the absence of any neuronal or glial influences, for > 100 doublings without any sign of senescence. The present study is focused on the expression of beta-adrenergic receptors on BBECs. By Northern blot hybridization, subtypespecific ligand binding, and cyclic AMP accumulation experiments, we demonstrate that beta-1- and beta-2-adrenergic receptors are coexpressed (in the respective proportions of 42 and 58%) on BBEC membranes and are functionally coupled to adenylate cyclase. This is the first report documenting a significant number of beta-1-adrenergic receptors on brain capillary endothelial cells. The results are discussed in light of the known noradrenergic innervation of brain capillaries.