Ring formation by human variant endothelial cells in vitro.

Variant endothelial cells were cultured from the healthy carotid arteries of a 19-year-old woman who was killed accidentally. The cells were grown and subcultured in Medium 199 supplemented with 20% heat-inactivated fetal calf serum. The cells are still viable after 20 passages. They were recognized as variant endothelial cells by their morphology which included ring formation, and by the existence of factor VIII-related surface antigen on the cell membrane. The cultured endothelial cells produced prostacyclin when the cells were incubated with arachidonic acid in smaller amounts than does typical endothelium, but far in excess of that produced by vascular smooth muscle cells.