- A group of α2-globulins in human serum, so called because of their ability to combine with hemoglobin, preventing loss in the urine; variant types form a polymorphic system, with α- and β-polypeptide chains controlled by separate genetic loci. Levels are decreased in hemolytic disorders and increased in inflammatory conditions or with tissue damage. [G. hapto, to grasp, + hemoglobin]
* * *hap·to·glo·bin 'hap-tə-.glō-bən n any of several forms of an alpha globulin found in blood serum that can combine with free hemoglobin in the plasma and thereby prevent the loss of iron into the urine
* * *n.a protein present in blood plasma that binds with free haemoglobin to form a complex that is rapidly removed from the circulation by the liver. Depletion of plasma haptoglobin is a feature of anaemias in which red blood cells are destroyed inside the circulation with the release of haemoglobin into the plasma and its loss in the urine.
* * *hap·to·glo·bin (hap″to-gloґbin) a 100,000-dalton plasma glycoprotein with alpha electrophoretic mobility that irreversibly binds free hemoglobin to form a hemoglobin-haptoglobin complex, which is promptly removed by the liver; this prevents loss of free hemoglobin in the urine. Haptoglobin levels are decreased by hemolysis and increased by increased synthesis in conditions resulting in extensive tissue damage and necrosis. Haptoglobin has two major genetic variants, designated Hp 1 and Hp 2.
Medical dictionary. 2011.