Secretory function of vascular endothelium and its implication in the action of vasoactive drugs

Monolayer of endothelial cells is no longer considered as a plain mechanical barrier which separates blood from the rest of our body. Endothelium became recognised as a powerful generator of substances which, by interaction with blood cells or blood plasma maintain homeostasis in the circulation [2, 4, 5, 10, 26, 38, 47, 60, 65, 66]. Generation of the above substances is regulated from inside and outside of the endothelial monolayer. E.g., the generation of prostacyclin is stimulated either by a transfer of prostaglandin endoperoxides from platelets, by contact with activated leukocytes, by an increase in plasma level of bradykinin or endothelins, by a change of blood pO2, or by a damage to or distension of vascular wall. Some of the above factors are interlocked with concomitant release of prostacyclin, EDRF, endothelin I and tissue plasminogen factor [11]. Two components of the endothelial secretory system i.e. prostacyclin and EDRF, have been chosen to be reviewed here.