Gastrin is one of the best studied gut hormones. It occurs in the circulation in several different forms, among those gastrin-34 and gastrin-17, sulphated and non-sulphated.
The determination of gastrin is useful in the diagnosis of gastrin-producing tumours and of achylia with or without pernicious anemia. In all these clinical situations the serum gastrin concentration is high. Treatment with powerful antisecretagogues may cause a rise in the serum gastrin concentration, because of an impaired acid feedback inhibition of gastrin release. Measurement of serum gastrin can thus be used to monitor the treatment with antisecretagogues.
Normal level of gastrin in human serum: 60 pmol/L (fasting level obtained with this procedure).
Mean value: 25 pmol/L +/- 10 pmol/L (1SD).
Range: 11-54 pmol/L.
The intended use of these reagents is for assay of gastrin in human serum.
For professional use within a laboratory.
Gastrin and the vagal nerves are the main regulators of gastric acid secretion. However other factors than gastrin contribute to the gastric acid secretion. The main site for gastrin production is the antropyloric mucosa of the stomach. A few gastrin producing cells may also be found in the duodenum and pancreas.
Gastrin occurs in many different forms in human serum. An amidated C-terminal is essential for the biological activity of the gastrins.
Progastrin is cleaved from preprogastrin. It has been shown that progastrin is partially sulphated in the tyrosine residues. The progastrin is enzymatically cleaved to the main circulating forms of biologically active gastrin: gastrin-34 and gastrin-17, which occur in sulphated an non-sulphated forms. Small amount of gastrin-52 (also named component 1), gastrin-14 (mini-gastrin) and even smaller fragments have been detected in serum.
Gastrin in serum is assayed by a competitive radioimmunoassay using a rabbit antiserum raised against a gastrin 17 albumin conjugate. Gastrin in standards and samples compete with 125I-labelled gastrin-17 in binding to the antibodies. 125I-gastrin binds in a reverse proportion to the concentration of gastrin in standards and samples. Antibody-bound 125I-gastrin is separated from the unbound fraction using the double antibody - polyethyleneglycol precipitation technique. The radioactivity of the precipitates is measured. The antiserum used in this assay crossreacts with gastrin-34 and the sulphated forms of gastrin-17 and gastrin-34.
The reagents provided in each kit are sufficient for 100 tubes.
1. Anti-gastrin (Reagent A)
Rabbit antiserum raised against synthetic human gastrin-17 conjugated to bovine serum albumin, 21 mL antiserum. Diluent: 0.05 M phosphate buffer, pH 7.4, 0.25% human serum albumin and 0.05% sodium azide. Colour: Yellow.
For 100 tubes.
2. 125I-Gastrin (Reagent B)
Contains 66 KBq or 1.8 Ci at reference date. Synthetic human gastrin-17 is iodinated.
The monoiodinated form is purified by HPLC.
Specific activity: 1700-2100 Ci/nmol (62-77 MBq/nmol). Lyophilized in 2.5 mL 0.5M phosphate buffer, pH 7.4, with 2.5% human serum albumin and 0.5% sodium azide.
Contains 0.12 mL normal rabbit serum. Colour: Blue.
Reconstitution in 25 mL distilled water.
3. Double antibody-PEG (Reagent C)
50 mL diluted goat anti-rabbit Ig antiserum in 0.05 M phosphate buffer, pH 7.4, 0.25% human serum albumin and 0.05% sodium azide.
Contains 5.0% (w/v) polyethylene glycol 6000. Colour: Red
4. Assay buffer (Reagent D)
40 mL 0.05 M phosphate buffer, pH 7.4, with 0.25% human serum albumin and 0.05% sodium azide.
5. Gastrin standard (Reagent E)
Lyophilized. 5.00 mL standard after reconstitution. Concentration : 500 pmol/L.
The standard is produced from synthetic human gastrin-17. Diluted in 0.05 M phosphate buffer, pH 7.4, 0.25% human serum albumin, 0.05% sodium azide.
Reconstitution in 5.00 mL distilled water.
6. Controls (Reagent F-G)
Lyophilized serum pools with low (normal) and high concentration of gastrin. 1.00 mL of each control after reconstitution.
Store all reagents at 2-8° C before reconstitution and use. The stability of the reagents is indicated on the labels of the vials. For lyophilized reagents the expiry date is valid for the unreconstituted reagents. The reconstituted reagents are stable for 8 weeks if stored properly.
The water used for reconstitution of lyophilized reagents should be distilled in an all-glass apparatus or be of corresponding purity. Dissolve the content in a vial by gentle inversion and avoid foaming.