Cellular and molecular mechanisms of endothelial cell dysfunction.

repeated observation that it is altered by a variety of pathophysiological conditions. Such alterations of NO production and/or bioavailability have been shown to occur both in experimental animal models and in human subjects, in the setting of such diverse disorders as hypertension, hypercholesterolemia, aging, cigarette smoking, diabetes, and heart failure (1). The mechanisms underlying the alteration of this important function of the endothelium are varied and likely multifactorial. During the past several years an enormous amount of research has been devoted to understanding these abnormalities, which has led to new insights into regulation of vascular tone, redox state, inflammation, growth, and the prothrombotic/antithrombotic properties of the vessel wall. This Perspective will highlight some of these important new observations, as they relate to the pathology of the endothelial cell L -arginine/NO synthase (NOS) system. In addition, future directions of research that may be particularly informative will be indicated. Alterations of the substrate for the NOS enzyme The substrate for NOS is the basic amino acid L -arginine (with a K m of approximately 5 m M, reference 2). L -Arginine is syn