To understand the hormonal regulation of saliva production, it is necessary to investigate how these chemical mediators cross the endothelial barrier from the systemic circulation. As a probe to study such an event, capillary endothelial cells have been isolated and established into a stable cell line. These cells grow in a relatively simple media, form specialized intercellular connections and eventually generate macroscopic capillry-like structures. The ready availability of such cells, capable of capillary formation in vitro in the absence of added factors, constitute a simplification for cell biological and biochemical studies and provide a model system where capillary proliferation is thought to play a central role in pathophysiology.