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The amino acid l-arginine and nitric oxide share a mutual relationship that is integral to human health. L-arginine helps to create urea, assisting in the elimination of harmful ammonia from the body, and has several key roles in immunity, healing, and cellular division. Nitric oxide is a molecule used for cells to signal to one another, and causes blood vessels to dilate, among several other functions.
L-arginine is used by the body to help produce nitric oxide. Enzymes known as nitric oxide synthases (NOSs) convert this amino acid into the gaseous signaling molecule. L-arginine and nitric oxide are utilized by the body in different amounts, and the action of NOSs in different bodily tissues is carefully regulated.
Like many processes in the body, the production of nitric oxide involves a negative feedback loop. After this molecule is created, it inhibits the activity of the NOS enzymes. This prevents cells from creating too much nitric oxide, and may play a role in some health problems. Nitric oxide is a reactive molecule, and can cause oxidative stress to cells, resulting in potentially serious problems with blood vessels.
NOSs in endothelial cells that line the blood vessels constantly utilize l-arginine and nitric oxide. These enzymes use oxygen and l-arginine to produce this cell signaling molecule. Nitric oxide can then be released by the cells into the bloodstream, where it causes the smooth muscle along the blood vessels to relax. This process dilates, or opens up, the blood vessels.
The ability to rapidly dilate blood vessels serves several purposes. It lowers blood pressure by providing a larger space for blood to travel through. Dilation also is essential for proper sexual functioning. Increased blood flow to the capillaries in the genitals allows for a normal sexual response.
Therapies for some medical conditions involve the relationship between these two compounds. Heart disease, clogged arteries, and some chest pain can improve through the administration of l-arginine. This happens because the resulting nitric oxide production and blood vessel dilation relieve the symptoms of these problems. Alternately, nitric oxide may be administered for these conditions, with similar results.
Conventional erectile dysfunction drugs generally do not use the l-arginine and nitric oxide pathway to improve blood flow. Research has been performed using l-arginine supplements for this condition, however. L-arginine was administered with two other compounds, glutamate and yohimbine, in the study. Results showed that this combination was successful in treating erectile dysfunction.