Description
Principle of the assay: This assay employs the competitive inhibition enzyme immunoassay technique. An antibody specific for INS has been pre-coated onto a microplate. Standards or samples and a biotin - conjugated antibody specific for INS are pipetted into the wells. A competitive inhibition reaction is launched between INS (Standards or samples) and biotin-conjugated INS with the pre-coated antibody specific for INS. After washing, streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of INS bound in the initial step. The color development is stopped and the intensity of the color is measured.
Background: Insulin is a polypeptide hormone originating in the beta cells of the pancreas and serving as a principal regulator for the storage and production of carbohydrates. Its secretion is normally stimulated by increases in the amount of glucose in circulation. This leads to higher insulin levels and more rapid tissueassimilation of glucose followed by a decline in the insulin level as the glucose level subsides. In a number of conditions, notably insulinoma and diabetes, this relationship is impaired. Insulin tends to circulate at inappropriately high levels in patients with insulin-secreting pancreatic tumors; such tumors can thus be a cause of hypoglycemia. Accordingly, insulin immunoassays used sometimes in connection with provocative doses of tolbutamide or calcium play an essential role in the identification (and localization) of insulinomas