Endothelial cells from bovine adrenal medulla develop capillary-like growth patterns in culture

The endocrine barrier between chromaffin cells and the blood stream in the adrenal medulla is made of capillary endothelial cells. We have now succeeded in isolating endothelial cells from adrenal medullary tissue, which are probably derived from this barrier. These cells grow on plastic surfaces in the absence of special growth factors or collagen overlays and differentiate into organized structures quite similar to true capillaries. The cells contain factor VIII:R, a marker for endothelial cells, and form intercellular junctions characteristic of capillary endothelial cells. They also synthesize and secrete basal lamina structures and engage in transcytosis, a characteristic ultrastructural and functional combination of exocytosis and endocytosis across the thin endothelial cell processes. These endothelial cells can take up and deaminate catecholamines by A-type monoamine oxidase, an enzyme functionally distinct from the B-type monoamine oxidase found in chromaffin cells. These data indicate that the chromaffin cell and its endothelial cell neighbor may constitute the functional unit of catecholamine metabolism in the adrenal medulla.