The endothelium plays a fundamental role in the blood coagulation cascade and at the site of injury is important in the development, and sequela, of atheroma. It is also now firmly established that endothelial cells can produce both vasorelaxant and vasoconstrictor factors and thus directly influence vascular tone and blood flow. Prostacyelin and NO are both potent vasodilators, and endothelin is a highly potent 21 amino acid peptide vasoconstrictor, which have all been shown to be syn The endothelium plays a fundamental role in the blood coagulation cascade and at the site of injury is important in the development, and sequela, of atheroma. It is also now firmly established that endothelial cells can produce both vasorelaxant and vasoconstrictor factors and thus directly influence vascular tone and blood flow. Prostacyelin and NO are both potent vasodilators, and endothelin is a highly potent 21 amino acid peptide vasoconstrictor, which have all been shown to be syn