The brain capillary endothelium is the main constituent of the blood-brain barrier. This study demonstrates that various vasoconstrictive peptides evoke dissimilar responses in the endothelial cells derived from human brain (HBEC) and human umbilical vein (HUVEC). Samples of human brain surgically removed for the treatment of idiopathic epilepsy served for isolation of HBEC, whereas HUVEC were obtained commercially. Both types of cells were characterized as endothelium (>98%) by positive staining for Factor VIII-related antigen and negative staining for GFAP and other non- endothelial markers. Vasoconstrictive peptides [endothelin-1 (ET-1), arginine-vasopressin (AVP), angiotensin II (Ang II)] markedly stimulated a transient (1-15 min) increase in IP3 formation [EC50 (ET-1
