Endothelium-derived relaxant factor EDRF

Furchgott and Zawadzki [1] first discovered that endothelial cells release a substance(s) responsible for the relaxation of vascular smooth muscle by acetylcholine this substance was named endothelium-derived relaxing factor (EDRF). This epoch-making discovery answers the question raised for nearly one hundred years by pharmacologists about why vascular smooth muscle is relaxed by acetylcholine, which however elicits contraction of the other smooth muscles. Because of its instability, the true chemical nature of EDRF was not easily identified. Several years later, several research groups independently found that the biological activities and biochemical properties of EDRF were identical... 

The results of a number of studies demonstrate that the gas nitric oxide (NO) plays a functional role in the central nervous system. This all originated with the discovery that the so-called endothelium-derived relaxing factor (EDRF), found in blood vessels, and thought to be a peptide, was in fact NO. The potential roles of this freely diffusible gas have subsequently been extended to many other tissues and organs but we will concentrate on the possible neuronal roles of what is obviously a novel mediator. There are also suggestions that the closely related carbon monoxide may also have a function in the central nervous system. 

A relationship between polyol pathway activity and reduction in endothelium-dependent relaxation in aorta from chronic STZ-diabetic rats has recently been reported (Cameron and Cotter, 1992). In agreement with several previous studies (Oyama et al., 1986 Kamata et al., 1989), endothelial-dependent relaxation was defective in the diabetic rats but the deficit was prevented by prior treatment with an AR inhibitor. The mechanism underlying the defect has been speculated to be due to decreased production of endothelium-derived relaxing factor (EDRF) or nitric oxide, NO (Hattori et al., 1991). It has been speculated that these vascular abnormalities may lead to diminished blood flow in susceptible tissues and contribute to the development of some diabetic complications. NO is synthesized from the amino-acid L-arginine by a calcium-dependent NO synthase, which requires NADPH as a cofactor. Competition for NADPH from the polyol pathway would take place during times of sustained hyperglycaemia and... 

NO (molecular weight = 30) is small but plays a big role in physiological regulation, not least in the vasculature where its effects were first seen (see Chapter 4). Endothelium-derived relaxation factor (EDRF) was discovered its ability to cause dilatation of vessels by relaxing the arterial muscle layer. Only much later was EDRF discovered to be a gas, nitric oxide. More recent interest in NO is based on the evidence that it is antiatherogenic. The pathogenesis of atherosclerosis is complex but many of the known effects of NO can be implicated in this common and serious condition. 

Tracey, W. R., Linden, J., Peach, M. J., and Johns, R. A. (1991). Comparison of spectro-photometric and biological assays for nitric oxide (NO) and endothelium-derived relaxing factor (EDRF) Nonspecificity of the diazotization reaction for NO and failure to detect EDRF. J. Pharmacol. Exp. Ther. 252, 922-928. 

Ignarro, L. J., Buga, G. M., Byms, R. E., Wood, K. S., and Chaudhuri, G. (1988a). Endothelium-derived relaxing factor (EDRF) and nitric oxide (NO) possess identical properties as relaxants of bovine arterial and venous smooth muscle. J. Pharmacol. Exp. Ther. 246, 218-226. 

Glomerular endothelial cells are able to produce endothelin and endothelium-derived relaxing factor (EDRF), synthesize and release von Willebrand factor,... 

---