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Horm Metab Res 1985; 17(11): 595-597
DOI: 10.1055/s-2007-1013615
Clinical

© Georg Thieme Verlag, Stuttgart · New York

Determination of Free-Insulin in Antibody Containing Sera: Comparison of Polyethylene Glycol and Staphylococcus Aureus Cells

D. L. Hwang, G. Barseghian, A. Lev-Ran
  • Department of Endocrinology, City of Hope Medical Center, Duarte, California, U.S.A.
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Publication History

1983

1984

Publication Date:
14 March 2008 (online)

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Summary

Polyethylene glycol (PEG) and killed Staphylococcus aureus cells (S. aureus) were used as agents to separate free insulin from antibody-bound insulin in diabetic sera. Insulin was determined by conventional double antibody radioimmunoassay. The free insulin values after PEG treatment were almost half of those after S. aureus treatment.

The free insulin levels in high-antibody containing sera preincubated at 37° C, 2 h were double the value of fresh sera. PEG treatment caused about 40% loss of total serum protein. The addition of bovine serum albumin (BSA) to the PEG-treated serum greatly increased the immunoreactive insulin values. This may suggest that protein concentration plays a role in insulin radioimmunoassay. PEG treatment may also enhance the interaction between free insulin and free antibodies resulting in underestimation of free insulin level.

Key-Words:

Free Insulin - Polyethylene Glycol - Staphylococcus Aureus