Protein A-sepharose used to measure free insulin in plasma

1991 ◽  
Vol 37 (1) ◽  
pp. 64-67 ◽  
Author(s):  
Didler Chevenne ◽  
Franclne Valade ◽  
Marle-Pascal Bridel ◽  
Odlie Rigal ◽  
Jean-Francols Demelier ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Insulin Therapy ◽  
Binding Capacity ◽  
Protein A ◽  
Insulin Antibodies ◽  
New Method ◽  
Diabetic Patients ◽  
Insulin In Plasma ◽  
Free Insulin

Abstract Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma. We describe a new method for removing such antibodies, with the use of Protein A coupled to Sepharose microspheres. The results correlate well with those by the PEG method, although values are systematically higher or lower for given samples, according to the initial titer of the antibody measured in terms of binding capacity. Further studies are required to clarify this observation.

Free and total insulin as determined after precipitation with polyethylene glycol: analytical characteristics and effects of sample handling and storage.

1987 ◽  
Vol 33 (1) ◽  
pp. 93-96 ◽  
Author(s):  
H Arnqvist ◽  
P O Olsson ◽  
H von Schenck
Keyword(s):  
Polyethylene Glycol ◽  
Room Temperature ◽  
Serum Samples ◽  
Sample Handling ◽  
Insulin In Plasma ◽  
Analytical Recovery ◽  
Free Insulin ◽  
Assay Precision ◽  
And Storage ◽  
Collection Time

Abstract We evaluated results of radioimmunoassays of free and total insulin after precipitation of endogenous antibodies with polyethylene glycol (PEG), and we investigated the influence of collection time, temperature, and storage in heparin- cr EDTA-treated plasma or serum on results for free insulin. Analytical recovery of free insulin was 99.3%, of total insulin 96.4%. For free insulin, assay precision (CV) was 4.0-13.0% (intra-assay) and 7.8-10.7% (inter-assay); for total insulin, 3.6-9.5% and 6.6-11.7%, respectively. Free insulin decreased in plasma (p less than 0.05) and serum (p less than 0.01) at room temperature after 3 h and in promptly analyzed serum (p less than 0.01). Storage of samples at -20 degrees C increased the concentration of free insulin in plasma (p less than 0.025) and serum (p less than 0.005), whereas the free insulin content of supernates after PEG precipitation was stable, except for a slight decrease in serum samples (p less than 0.02). We conclude that, for radioimmunoassay of free and total insulin, plasma should be used, treated with PEG without delay; supernates then are analytically stable for as long as 26 weeks at -20 degrees C.

Quantitation of Free, Total, and Antibody-bound Insulin in Insulin-Treated Diabetics

1975 ◽  
Vol 21 (7) ◽  
pp. 873-879 ◽  
Author(s):  
William D Gennaro ◽  
John D Van Norman
Keyword(s):  
Polyethylene Glycol ◽  
Insulin Antibodies ◽  
Immunoreactive Insulin ◽  
Simplified Method ◽  
Free Insulin ◽  
Antigen Complex ◽  
The Difference ◽  
Glycol Solution

Abstract We describe a simplified method for measuring free, total, and antibody-bound insulin in insulin-treated patients in whom antibodies to insulin are present. The free, active insulin is extracted from the serum with a polyethylene glycol solution. Total insulin is extracted from the serum with a polyethylene glycol solution after dissociation of the antibody—antigen complex with dilute HCl. Aliquots of the extracts are used in the radioimmunoassay system. The figure for antibody-bound insulin is the difference between the total and free insulin values and reflects the concentration of insulin antibodies present. A commercially available ("Phadebas") radioimmunoassay for immunoreactive insulin was used to quantitate the insulin present in the two extracts. Recovery of added insulin averaged 85% for the free insulin and 87% for the total insulin.

Insulin Therapy in Uremic Diabetic Patients on Continuous Ambulatory Peritoneal Diaysis; Comparison of Intraperitoneal and Subcutaneous Administration

1994 ◽  
Vol 14 (2) ◽  
pp. 127-131 ◽  
Author(s):  
Lino Scarpioni ◽  
Sergio Ballocchi ◽  
Aurelio Castelli ◽  
Roberto Scarpioni
Keyword(s):  
Blood Glucose ◽  
Glycemic Control ◽  
Insulin Therapy ◽  
Subcutaneous Administration ◽  
Diabetic Patients ◽  
Insulin Administration ◽  
Good Glycemic Control ◽  
Free Insulin ◽  
Insulin Dependent Diabetic ◽  
Beta Hydroxybutyrate

Objective To compare, in diabetic uremic patients on continuous ambulatory peritoneal dialysis (CAPD), the effects of two patterns of insulin administration, four times daily subcutaneous (SC) injections and intraperitoneal (IP) route, on blood glucose, insulin, lactate, beta-hydroxybutyrate and glycerol levels. Patients and Methods We examined 6 uremic insulin-dependent diabetic patients on CAPD. The two insulin regimens, SC and IP, were tested successively in randomized sequence in each patient. At the end of each treatment period we determined the 24-our profiles of blood glucose, free insulin, lactate, beta-hydroxybutyrate, and glycerol. Results Mean blood glucose over 24 hours (SC 7.21 ±0.61 mmol/L, IP 7.49±0.93 mmol/L), Schlichtkrull's M value, an index of glycemic control and stability (SC 10±3, IP 10±5), and the blood intermediate metabolites beta-hydroxybutyrate, lactate, and glycerol were similar in both groups. Mean serum free insulin was significantly higher during subcutaneous treatment (SC 257. 4±127.2 pmol/L, IP 170.4±83.4 pmol/L, p < 0.001). Insulin requirements were 2.5 times greater for the intraperitoneal route (SC 51 ±4 U/24 hours, IP 130±43 U/24 hours). Conclusions In uremic diabetic patients on CAPD, good glycemic control may be achieved either with subcutaneous intensive insulin therapy or with intraperitoneal insulin administration. The latter method allows reduction of circulating free insulin levels, but requires a higher dose of insulin per day.

Measurement of Antibodies to Insulin in Serum

1974 ◽  
Vol 20 (10) ◽  
pp. 1275-1281 ◽  
Author(s):  
K Dixon
Keyword(s):  
Binding Capacity ◽  
Insulin Antibodies ◽  
Insulin Antibody ◽  
Affinity Constant ◽  
Simple Extension ◽  
Antibody Assay ◽  
Insulin In Serum ◽  
Free Insulin ◽  
Maximum Binding Capacity

Abstract I describe a method for measuring insulin antibodies in insulin-treated subjects. The antibodies are characterized by maximum binding capacity and affinity constant. Endogenous and therapeutic insulin interferes in insulin antibody assay, and it is removed by dextran—charcoal treatment at pH 3.5. Endogenous total and free insulin may be measured by a simple extension of the method.

Diagnosis of self-induced hyperinsulinism in an insulin-dependent diabetic patient by radioimmunoassay of free C-peptide.

1981 ◽  
Vol 27 (1) ◽  
pp. 184-186 ◽  
Author(s):  
M T Meistas ◽  
M S Kumar ◽  
O P Schumacher
Keyword(s):  
Polyethylene Glycol ◽  
Diabetic Patient ◽  
Insulin Antibodies ◽  
Self Administration ◽  
C Peptide ◽  
Free Insulin ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic ◽  
Antigen Antibody ◽  
Plasma Free Insulin

Abstract On the basis of results of simultaneous determinations of plasma free insulin and free c-peptide, episodes of hypoglycemia in an insulin-dependent diabetic were attributed to surreptitious self-administration of insulin. Immunoreactive c-peptide values were falsely increased and diagnostically misleading when measured in unextracted plasma. After preliminary removal of antigen/antibody complexes from the plasma by extraction with polyethylene glycol, the c-peptide values, referred to as "free c-peptide," were suppressed. We suggest that insulin antibodies formed complexes with proinsulin-like material in the plasma of this patient, which accounted for most of the c-peptide immunoreactivity in her unextracted plasma. These complexes must be removed if c-peptide measurements are to be accurate.

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