The purpose of the test is determination of somatostatin in human plasma. Somatostatin in plasma is extracted with Sep-pak C18 cartridges. The extracts are analysed by a competitive radioimmunoassay using an antiserum to synthetic cyclic somatostatin 14. Somatostatin in standards and samples compete with 125I-labelled somatostatin in binding to the antibodies. 125I-Tyr1-somatostatin binds in a reverse proportion to the concentration of somatostatin in standards and samples. Antibody-bound 125I-Tyr1-somatostatin is separated from the unbound fraction using the double antibody solid phase precipitation technique. The radioactivity of the precipitates is measured.
The result shall not be used for clinical diagnosis or patient management.
The reagents provided in each kit are sufficient for 100 tubes.
1. Anti-somatostatin (Reagent A)
Rabbit antiserum to synthetic cyclic somatostatin. The immunogen was cyclic somatostatin conjugated to bovine thyroglobuline. Lyophilized in 2.0 mL 0.5 M phosphate buffer, pH 7.4, 2.5% human serum albumin, 2.5% EDTA disodium salt and 0.5% sodium azide.
Reconstitution in 22 mL distilled water. The reconstituted reagent contains 500 KIU TrasylolÒ per mL. For 100 tubes. Colour: Yellow.
2. 125I-Somatostatin (Reagent B)
Total radioactivity: 28 KBq or 0.75 μCi. Produced by iodination of Tyr1-somatostatin. HPLC-purified, monoiodinated. Specific activity: 62-77 Mbq/nmol (1700-2100 μCi/nmol).
Lyophilized in 2.5 mL 0.5 M phosphate buffer, pH 7.4, 2.5% human serum albumin,
2.5% EDTA disodium salt and 0.5% sodium azide. Reconstitution in 25 mL distilled water. The reconstituted reagent contains 500 KIU TrasylolÒ per mL. Colour: Blue.
3. Double antibody solid phase (Reagent C)
11 mL suspension. Anti-rabbit-IgG coupled to cellulose particles.
4. Assay diluent (Reagent D)
50 mL 0.05 M phosphate buffer, pH 7.4 with 0.25% human serum albumin, 0.25% EDTA disodium salt, 0.05% sodium azide, 0.1% Tween 80 and 500 KIU TrasylolÒ per mL. To be used for the dilution of the somatostatin standard, reconstitution of sample extracts and instead of antiserum in non-specific binding controls.
5. Somatostatin standard (Reagent E)
5.0 mL, 250 pmol/L, synthetic cyclic somatostatin (MW = 1638.1). Lyophilized in 0.05 M phosphate, pH 7.4 with 0.25% human serum albumin, 0.25% EDTA disodium salt, 0.05% sodium azide and 500 KIU Trasylol® per mL. Reconstitution in 5.00 mL distilled water.
6. Controls (Reagent F-G)
Lyophilized controls with two different levels of somatostatin. 1.00 mL of each control after reconstitution. The somatostatin concentrations are given on the labels of the vials. The controls should be assayed directly without extraction. Contains 0.05% sodium azide.
Store all reagents at 2-8° C before reconstitution and use. The water used for reconstitution of the lyophilized reagents should be distilled in an all-glass apparatus or be of corresponding purity. Dissolve the contents in a vial by gentle inversion and avoid foaming. The stability of the reagents is found on the label of the vials. For lyophilized reagents the expiry date is valid for the unreconstituted reagents. Reconstituted reagents are stable for 10 weeks or until the expiry date is reached when stored according to the instructions.