[Gastrin radioimmunoassay with polyethylene glycol method]

Area of Science:

• Biochemistry
• Immunology
• Radiochemistry

Context:

• Gastrin is a key hormone regulating gastric acid secretion.
• Accurate measurement of gastrin levels is crucial for diagnosing and monitoring various gastrointestinal disorders.
• Existing radioimmunoassay methods may have limitations in sensitivity, specificity, or ease of use.

Purpose:

• To develop a highly sensitive and specific radioimmunoassay for human gastrin using 125I-labelled gastrin.
• To optimize the radioiodination process for gastrin to achieve high specific radioactivity and immunological activity.
• To validate the developed radioimmunoassay by assessing its precision, accuracy, and correlation with established methods.

Summary:

• A novel method for preparing 125I-labelled gastrin with high specific radioactivity (22.2–25.9 GBq/mg) was established using the chloramine-T method with a 100-fold molar excess of chloramine-T.
• The radioimmunoassay, employing polyethylene glycol (PEG) for separation, exhibited excellent intra-assay (3.6–7.6% C.V.) and inter-assay (5.7–10.4% C.V.) precision.
• The assay demonstrated high accuracy with average recoveries of 104% and 105% for two gastrin levels in serum, and showed strong correlation (r=0.973) with the dextran-coated charcoal (DCC) method.
• The antibody utilized specifically recognizes the tyrosin residue at position 12 and the methionyl residue at position 15 of gastrin (1-17), ensuring high specificity.

Impact:

• Provides a robust and validated radioimmunoassay for accurate gastrin measurement, aiding in clinical diagnosis and research.
• The high-specific-activity 125I-labelled gastrin tracer can enhance the sensitivity of gastrin detection.
• This method offers a reliable alternative or improvement over existing gastrin assays, potentially simplifying diagnostic procedures.