Haptoglobin in serum
Haptoglobin ( Hp) is a blood plasma glycoprotein that specifically binds Hb. There are three hereditary phenotypes of haptoglobin: Hp 1-1, 2-1, 2-2.The first form is a monomer with a molecular weight of 85,000, the other two are polymers with a varying but much larger mass. Haptoglobin 1-1 consists of 4 polypeptide chains: 2 lungs - a-chains and 2 heavy chains - p-chains, connected by di-sulfide bridges. The reference values of the concentration of haptoglobin in serum are given in Table.[Titz N., 1997].
Table Reference Haptoglobin Concentrations in the Serum
Table Reference Haptoglobin Concentrations in the Serum
The basic physiological function of haptoglobin is the preservation of iron in the body, in addition, the Hb-haptoglobin complex has a high peroxidase activity, exerting a retarding effect on lipid peroxidation processes.
Haptoglobin refers to the proteins of the acute phase. Increase in its concentration in the blood occurs due to stimulation of IL cells of the liver. Nevertheless, changes in the concentration of haptoglobin in the blood are not as regular as other proteins in the acute phase. This is due to the fact that when hemolysis in vivo, which often accompanies acute phase processes, haptoglobin selectively binds to free Hb plasma, which leads to a decrease in its content in the blood. Therefore, the overall result can be an increase, decrease or maintenance of the normal concentration of this protein. To exclude the effect of hemolysis on the results of the determination of haptoglobin, they must be compared with the data of a study of at least one other acute phase reactant. The main diseases and conditions leading to an increase in the concentration of haptoglobin in the blood serum are similar to those given for orosomucoid. In addition, an increase in the content of haptoglobin in the blood is observed with cholestasis, treatment of HA.
Reduction of haptoglobin concentration is detected in all types of hemolysis in vivo - autoimmune, isoimmune, mechanical( artificial heart valves, trauma, etc.);with acute and chronic liver diseases;with ineffective erythropoiesis( deficiency of folic acid, hemoglobinopathy);defects of the erythrocyte membrane or metabolism( deficiency of glucose-6-phosphate dehydrogenase);increased spleen.
In nephrotic syndrome, the degree of decrease in the concentration of haptoglobin in the blood depends on its phenotype. With Hp 1-1, whose molecular mass is relatively small, the concentration of haptoglobin decreases due to its losses in the urine. With other types of haptoglobin( with a higher molecular mass), losses with urine do not practically occur and its concentration in the blood does not decrease.
The content of haptoglobin in the blood serum increases with malignant neoplasms of some localizations( breast, gastrointestinal, genital, lung, etc.).It is possible to change the relative content of types of haptoglobin in the serum of patients with genital and breast cancer( predominance of Hp 1-1 in malignant tumors of the mammary gland and decrease in Hp 2-2 in cervical cancer).