预期应用

    ELISA法定量测定小鼠血清、血浆、细胞培养物上清或其它相关液体中PI含量。

 

实验原理

    本试剂盒应用双抗体夹心酶标免疫分析法测定标本中PI水平。用纯化的抗体包被微孔板，制成固相抗体，往包被单抗的微孔中依次加入PI抗原、生物素化的抗小鼠PI抗体、HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的PI呈正相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。

 

Intended use

   This immunoassay kit allows for the specific measurement of mouse Proinsulin concentrations in cell culture supernates, serum, and plasma.

 

Introduction

    Proinsulin is synthesized in the pancreatic beta cells as a 9390 mw polypeptide of 86 amino acids. Proinsulin is subsequently cleaved enzymatically, releasing insulin into the circulation along with a residual 3000 mw fragment called C-peptide, so-named because it connects the A and B chains of insulin within the proinsulin molecule.

Proinsulin, which has relatively low biological activity (approximately 10% of insulin potency), is the major storage form of insulin. Normally, only small amounts (~3% of the amount of insulin, on a molar basis) of proinsulin enter the circulation. Because the hepatic clearance of proinsulin is only 25% of insulin clearance, the half-life of proinsulin is two- to threefold longer and concentrations in the fasting state are approximately 10% to 15% of insulin concentrations.

High proinsulin concentrations have been associated with benign or malignant β-cell tumors of the pancreas4 and endocrine pancreatic tumors associated with MEN. Elevated proinsulin levels have been observed in individuals with impaired glucose tolerance even in the absence of abnormal glucose or C-peptide levels. Elevated proinsulin levels have been found to be a positive risk factor for the development on NIDDM. Most patients with β-cell tumors have increased insulin, C-peptide, and proinsulin concentrations, but occasionally only proinsulin is elevated. Despite its low biological activity, proinsulin may be increased sufficiently to produce hypoglycemia. In addition, a rare form of familial hyperproinsulinemia, due to impaired conversion to insulin, has been described. Increased proinsulin concentrations may also be detected in patients with chronic renal failure, cirrhosis, or hyperthyroidism.

 

Test principle

    This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for Proinsulin has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any Proinsulin present is bound by the immobilized antibody. An enzyme-linked monoclonal antibody specific for Proinsulin is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of Proinsulin bound in the initial step. The color development is stopped and the intensity of the color is measured.