THE ROLE OF ENDOTHELIUM DERIVED RELAXATION FACTOR (EDRF) IN VASCULAR TONE CONTROL

Ever since Thomas Lauder - Bruton First introduced Amylnitrate into clinical medicine, nitrovasodilators of different classes have been extensively used in the medical treatment of angina pectoris, myocardial infarction and heart failure. Understanding the mechanisms of action of nitrates has been greatly expanded in the last decade, particularly since the discovery of endothelium dependent relaxation and its mediator, the endogenous nitrate, NO.
In present research, by using perfusion, isolated vessels 'ring (in-vitro) and laser Doppler flowmetry, (LDF) in-vivo techniques, the effect of some vasoactive substances and vascular nervous system were studied in present and absent of endothelium. Substances such as Adenosine, Adenosine triphosphate (ATP) and Acetylcholine (Ach) induced their vasodilation effect via endothelium. These responses were dose dependent.
The vasoconstriction effect which followed, after nervous stimulation or vasoactive substances such as adrenergic agonists (clonidine, adrenaline and epinephrine) were augmented 60-100 percent, when NO. Synthesis was blocked by Nw-Nitro-I-arginine methyl-ester (L-NAME). This response was reversed by L-Arginine which induced NO synthesis.
These results showed that ednothelium has role in modulation of vasoactivity of blood vessels due to stimulation of sympathetic nerves or endogenous substance in blood by releasing NO.