[The role of the endothelium in normal and pathological vascular reactivity]

After a short incursion concerning the morpho-chemical characteristics of the vascular endothelium, the main normal and pathological functional implications of the endothelial vasoactive substances are reviewed. A special attention is given to the myorelaxing effects of EDRF, identified as nitrogen oxide (NO) and its production mechanism, at the vascular level, with the participation of cGMP as intracellular second messenger. The literature data are completed by a part of the personal research regarding the changes of the vascular reactivity induced by the endothelial NO. Experimental proves are brought in favor of influencing of the vasconstrictor reactions produced by phenylefrin, noradrenalin and angiotensin by the NO-cGMP system. Finally, the main patho-physiological and pharmacological implications of endothelial NO are mentioned.