of, relating to, or of the nature of preference: preferential policies. 2. showing or giving preference: a preferential hiring system. 3. receiving or enjoying preference, as a country in trade relations; favored. Origin of preferential.
Histamine dilates post-capillary venules, activates the endothelium, and increases blood vessel permeability. This leads to local edema (swelling), warmth, redness, and the attraction of other inflammatory cells to the site of release. It also depolarizes nerve endings (leading to itching or pain).
Mast cells. Most histamine in the body is generated in granules in mast cells and in white blood cells called basophils and eosinophils. Mast cells are especially numerous at sites of potential injury â the nose, mouth, and feet, internal body surfaces, and blood vessels.istamine base, obtained as a mineral oil mull, melts at 83-84 Â°C. Hydrochloride and phosphorus salts form white hygroscopic crystals and are easily dissolved in water or ethanol, but not in ether. In aqueous solution, histamine exists in two tautomeric forms: NÏ-H-histamine and NÏ-H-histamine.