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).
Storage and release. Histamine is found in almost all bodily tissues, mainly stored inside the granules of mast cells, where it is bound to compounds such as heparin. Mast cells are abundant in tissues that are prone to injury such as the extremities and blood vessels.Blood cells called basophils also contain some granules that have histamine inside them. The plasma concentration of histamine is less than 1 mg/L, although it may be higher in patients who have asthma.he increased permeability of blood vessels allows immune cells and substances to migrate from the bloodstream, through the vessels and into the site where injury or infection has occurred. Leukocytes and blood plasma proteins can then begin the process of fighting infection and healing the tissue.