VASCULAR ORIGIN DETERMINES ANGIOTENSIN I-CONVERTING ENZYME EXPRESSIONIN ENDOTHELIAL-CELLS

Previous observations on the heterogeneous distribution of von Willebr and factor in the vascular endothelium led us to examine the expressio n of angiotensin I-converting enzyme (ACE) in function of the vascular origin of endothelial cells (EC), EC from pig thoracic aorta, pulmona ry artery, inferior vena cava and brain capillaries were cultured and assayed for ACE by enzymatic radiochemical determination and by wester n-blot and immunofluorescence using an antiACE polyclonal antibody, EC from the various vascular levels secreted ACE in the culture medium; western-blot analysis showed its presence at cellular level and immuno fluorescence confirmed its location on the plasma membrane, But quanti fication revealed that EC from pulmonary artery contain more ACE than EC from the other vessels, especially from brain capillaries; immunofl uorescence correlated well with the functional data, In contrast, secr etion of ACE by brain capillaries EC was faster than that of arteries and of vena cava, the latter being the less effective, This differenti al ACE expression along the vascular tree could have a pharmacological implication since ACE inhibitors, used in the treatment of arterial h ypertension, may act more at the vascular level than on the plasma ren in-angiotensin system, On the other hand, endothelial distribution of ACE was different from that of von Willebrand factor; in particular we showed that EC cultured from vessels of pigs homozygous for the von W illebrand disease, in which von Willebrand factor synthesis was comple tely abolished, normally express ACE.