A simple and rapid method is presented for the preparation of I/sup 131/- labeled human growth hormone of high specific radioactivity (240-300 mu C/ mu g). Low amounts of carrierfree I/sup 131/ iodide (2 mC) are allowed to react, without prior treatment, with small quantities of protein (5 mu g) in a highyield reaction (approx. 70% transfer of I/sup 131/ to protein). The degree of chemical substitution is minimized (0.5- 1.0 atom of iodine/molecule of protein) by the use of carrier-free I/sup 131/ iodide. The I/sup 131/-labeled hormone (up to 300 mu C/ mu g) contains no detectable degradation products and is immunologically identical with the unlabeled hormone. The loss of immunological reactivity at high specific radioactivities or at high levels of chemical substitution with STAI/sup 127/!iodine is demonstrated. (auth)

The preparation of 131i-labelled human growth hormone of high specific radioactivity

Enzyme-linked immunosorbent assay (ELISA). Quantitative assay of immunoglobulin G.

1. A new method is described for labelling proteins to high specific radioactivities with (125)I. The protein is treated with a (125)I-labelled acylating agent, iodinated 3-(4-hydroxyphenyl)propionic acid N-hydroxysuccinimide ester, which reacts with free amino groups in the protein molecule to attach the (125)I-labelled groups by amide bonds. 2. Three protein hormones have been labelled by this method, human growth hormone, human thyroid-stimulating hormone and human luteinizing hormone. Specific radioactivities of up to 170, 120 and 55muCi/mug respectively have been obtained for these hormones. 3. The immunoreactivity of these labelled hormones has been investigated by using a radioimmunoassay system specific for each hormone. These preparations have also been compared with and found to be equal or superior to labelled hormones prepared by chemical substitution of (125)I into tyrosine residues of the proteins by using the chloramine-t-oxidation procedure. 4. With some antisera the immunoreactivity of the antigen was diminished by the introduction of a single I atom into the tyrosyl groups, whereas antigen containing a single (125)I-labelled 3-(4-hydroxyphenyl)propionamide group showed the same immunoreactivity as the unmodified antigen.

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The labelling of proteins to high specific radioactivities by conjugation to a 125I-containing acylating agent. Application to the radioimmunoassay

Hepatocyte growth factor (HGF) is a plasminogen-like protein thought to be a humoral mediator of liver regeneration A 145-kilodalton tyrosyl phosphoprotein observed in rapid response to HGF treatment of intact target cells was identified by immunoblot analysis as the beta subunit of the c-met proto-oncogene product, a membrane-spanning tyrosine kinase Covalent cross-linking of 125I-labeled ligand to cellular proteins of appropriate size that were recognized by antibodies to c-met directly established the c-met product as the cell-surface receptor for HGF

https://science.sciencemag.org/content/sci/251/4995/802.full.pdf

Identification of the hepatocyte growth factor receptor as the c-met proto-oncogene product

https://www.cell.com/cell/pdf/0092-8674(93)90573-9.pdf

High affinity VEGF binding and developmental expression suggest Flk-1 as a major regulator of vasculogenesis and angiogenesis.

RECENT procedures for the immunological assay of protein hormones in human plasma1–3 require the routine preparation of hormones labelled with iodine-131 of high specific activity.

W M Hunter

Papers

Preparation of Iodine-131 Labelled Human Growth Hormone of High Specific Activity