[Radioreceptor assay of insulin and detection of anti-insulin receptor antibody using human placenta and their clinical application].
A receptor assay system for human serum insulin and a method for detection of anti-insulin receptor antibody in human serum using human placental receptor were developed. The receptor assay system was sensitive enough to measure the fasting insulin level and not interfered by serum proteins. The method for detecting antibodies to the insulin receptor was interfered by the presences of serum insulin with a relatively high levels and anti-insulin antibodies in the direct incubation method in which serum and radioinsulin were incubated simultaneously, but the interference by anti-insulin antibody was avoided in the indirect incubation method in which the receptor incubated with serum was washed before incubation with radioinsulin. With these methods, patients with carbohydrate intolerance were investigated. The insulin levels measured with receptor assay were in exact accordance with the insulin levels measured with radioimmunoassay, and no anti-insulin receptor antibody was detected in sera from normal volunteers as well as diabetic patients. However, in three cases abnormality was observed. In the first case with hypoglycemia due to extrapancreatic tumor, a low insulin immunoreactivity and a high insulin-like activity (ILA) measured with receptor assay were observed. In considering the ILA in her serum, the presence of immunoinactive insulin-like substance with hypoglycemic action was speculated. In the second case with insulin resistant diabetes, later with hypoglycemia, a substance inhibiting the binding of radioinsulin to the placental receptor was detected. Since the substance was positive even after the adsorption of insulin with charcoal in the indirect incubation method, the presence of anti-insulin receptor antibody was speculated. In the third case with high insulin level despites with mild carbohydrate intolerance, the insulin values with radioimmunoassay and radioreceptor assay were coincident and no anti-insulin receptor antibody was detected. According to further studies using the erythrocytes receptor from this patient, a decrease of insulin receptor number was confirmed. The receptor assay system and receptor antibody detection method seems to be useful for investigating the pathogenesis of some patients with carbohydrate intolerance.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000906:Antibodies / Q000032:analysis*; D050260:Carbohydrate Metabolism; D003920:Diabetes Mellitus / Q000378:metabolism; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000378:metabolism; D007328:Insulin / Q000097:blood*; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011869:Radioligand Assay; D011972:Receptor, Insulin / Q000276:immunology*
D000906:Antibodies; D007328:Insulin; D011972:Receptor, Insulin