Tyrosine A14(/sup 125/I)monoiodoinsulin: preparation, biologic properties, and long-term stability
/sup 125/I-insulin was prepared by reacting 17.4 nmol porcine insulin (100 micrograms) with 5 mCi /sup 125/I (about 2.4 nmol) using the lactoperoxidase method. The reaction product was subjected to gel electrophoresis and the band containing A14 (/sup 125/I)monoiodoinsulin was eluted. This preparation showed a specific activity of about 1.5 Ci/mumol as evaluated by radioimmunoassay and bioassay, i.e., about 75% of the theoretical maximum. The content of radioactive derivatives other than A14 monoiodoinsulin was less than 2%. The binding affinity of tracer A14 monoiodoinsulin to adipocytes, hepatocytes, and cultured human lymphocytes was twice as high as that of A19 monoiodoinsulin. Binding to antibodies was examined to 10 guinea pig anti-insulin sera. Three sera did not distinguish between the two tracers, whereas seven exhibited higher binding of the A14 tracer. A detailed analysis of one of the discriminating sera showed that the average affinity constant was about 2.5 times lower for the A19 tracer than for the A14 tracer. The A14 monoiodoinsulin tracer is remarkably stable. After 200 days the specific activity had declined to about half of its original value which is consistent with the hypothesis that the physical decay of (/sup 125/I)monoiodoinsulin (T 1/2 equals 60 days) extinguishes the activity of the molecule without causing major damage of other molecules. By this time 96% of the radioactivity migrated with insulin when subjected to gel filtration on Sephadex G-50, 4% was in the void volume, and nothing in the total column volume or later. Binding to receptors was indistinguishable from that obtained at time zero. It is concluded that Tyr A14(/sup 125/I)monoiodoinsulin represents an advance in biologic work as compared with previous tracers for insulin.
- OSTI ID:
- 5615194
- Journal Information:
- Diabetes; (United States), Vol. 30:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
INSULIN
BIOCHEMISTRY
IODINE 125
TRACER TECHNIQUES
ANTIBODIES
CHEMICAL PREPARATION
LABELLED COMPOUNDS
RADIONUCLIDE KINETICS
STORAGE LIFE
TISSUE DISTRIBUTION
BETA DECAY RADIOISOTOPES
CHEMISTRY
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PEPTIDE HORMONES
RADIOISOTOPES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques
400702 - Radiochemistry & Nuclear Chemistry- Properties of Radioactive Materials