Rat Cholecystokinin (CCK) ELISA Kit
Catalog No. CSB-E08114r
(96 tests)
This immunoassay kit allows for the in vitro quantitative determination of rat CCK concentrations in serum, plasma.
Expiration date six months from the date of manufacture
FOR RESEARCH USE ONLY. NOT FOR USE IN DIAGNOSTIC PROCEDURES.
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INTRODUCTION
Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat a-n-d protein. Cholecystokinin, previously called pancreozymin, is synthesised by I-cells in the mucosal epithelium of the small intestine a-n-d secreted in the duodenum, the first segment of the small intestine, a-n-d causes the release of digestive enzymes a-n-d bile from the pancreas a-n-d gallbladder, respectively. It also acts as a hunger suppressant. Recent evidence has suggested that it also plays a major role in inducing drug tolerance to opioids like morphine a-n-d heroin, a-n-d is partly implicated in experiences of pain hypersensitivity during opioid withdrawal. CCK is composed of varying numbers of amino acids depending on post-translational modification of the CCK gene product, preprocholecystokinin. Thus CCK is actually a family of hormones identified by number of amino acids, e.g., CCK58, CCK33, a-n-d CCK8. CCK58 assumes a helix-turn-helix configuration. CCK is very similar in structure to gastrin, another of the gastrointestinal hormones. CCK a-n-d gastrin share the same five amino acids at their C-termini. CCK mediates a number of physiological processes, including digestion a-n-d satiety. Secretion of CCK by the duodenal a-n-d intestinal mucosa is stimulated by fat-or protein-rich chyme entering the duodenum. It then inhibits gastric emptying a-n-d gastric acid secretion a-n-d mediates digestion in the duodenum. It stimulates acinar cell of pancreas to release water a-n-d ions a-n-d stimulates the secretion of a juice rich in pancreatic digestive enzymes. Together these enzymes catalyze the digestion of fat, protein, a-n-d carbohydrates. Thus the levels of the substances which stimulated the release of CCK drop a-n-d the concentration of the hormone drops as well. The release of CCK is also inhibited by somatostatin. CCK also causes the increased production of hepatic bile, a-n-d stimulates the contraction of the gall bladder a-n-d the relaxation of the Sphincter of Oddi (Glisson's sphincter), resulting in the delivery of bile into the duodenal part of the small intestine. Bile salts form amphipathic micelles that emulsify fats, aiding in their digestion a-n-d absorption. As a neuropeptide, CCK mediates satiety by acting on the CCK receptors distributed widely throughout the central nervous system. In humans, it has been suggested that CCK administration causes nausea a-n-d anxiety, a-n-d weakly decreases the desire to eat is the reason for CCK administration to induce a satiating effect. Some studies have given a strong correlation for the satiating effect, but have not proven or disproven that CCK administration causes nausea or anxiety. The mechanism for this hunger suppression is thought to be a decrease in the rate of gastric emptying. CCK also has stimulatory effects on the vagus nerve, effects that can be inhibited by capsaicin. The stimulatory effects of CCK oppose those of ghrelin, which has been shown to inhibit the vagus nerve. The CCK tetrapeptide fragment CCK-4 (Trp-Met-Asp-Phe-NH2) reliably causes anxiety when administered to humans, a-n-d is commonly used in scientific research to induce panic attacks for the purpose of testing new anxiolytic drugs. The effects of CCK vary between individuals. For example, in rats, CCK administration significantly reduces hunger in young males, but is slightly less effective in older subjects, a-n-d even slightly less effective in females. The hunger-suppressive effects of CCK also are reduced in obese rats.
PRINCIPLE OF THE ASSAY
The microtiter plate provided in this kit has been pre-coated with an antibody specific to CCK. Sta-n-dards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody preparation specific for CCK a-n-d Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well a-n-d incubated. Then a TMB (3,3',5, 5' tetramethyl-benzidine) substrate solution is added to each well. Only those wells that contain CCK, biotin-conjugated antibody a-n-d enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution a-n-d the color change is measured spectrophotometrically at a wavelength of 450 nm ± 2 nm. The concentration of CCK in the samples is then determined by comparing the O.D. of the samples to the sta-n-dard curve.
DETECTION RANGE
15.6 pg/ml-1000 pg/ml. The sta-n-dard curve concentrations used for the ELISA’s were 1000 pg/ml, 500 pg/ml, 250 pg/ml, 125 pg/ml, 62.5 pg/ml, 31.2 pg/ml, 15.6 pg/ml.
SPECIFICITY
This assay recognizes rat CCK. No significant cross-reactivity or interference was observed.
SENSITIVITY
The minimum detectable dose of rat CCK is typically less than
3.9 pg/ml. The sensitivity of this assay, or Lower Limit of Detection (LLD) was defined as the lowest protein concentration that could be differentiated from zero.
MATERIALS PROVIDED STORAGE
| Reagent | Quantity | | Assay plate | 1 | | Standard | 2 | | Sample Diluent | 1 x 20 ml | | Biotin-antibody Diluent | 1 x 10 ml | | HRP-avidin Diluent | 1 x 10 ml | | Biotin-antibody | 1 x 120μl | | HRP-avidin | 1 x 120μl | | | 1 x 20 ml | | Wash Buffer | | | | (25×concentrate) | | TMB Substrate | 1 x 10 ml | | Stop Solution | 1 x 10 ml | |
1. Unopened test kits should be stored at 2-8?C upon receipt a-n-d the microtiter plate should be kept in a sealed bag. The test kit may be used throughout the expiration date of the kit, provided it is stored as prescribed above. Refer to the package label for the expiration date.
2. Opened test plate should be stored at 2-8?C in the aluminum foil bag with desiccants to minimize exposure to damp air. The kits will remain stable until the expiring date shown, provided it is stored as prescribed above.
3. A microtiter plate reader with a ba-n-dwidth of 10 nm or less a-n-d an optical density range of 0-3 OD or greater at 450nm wavelength is acceptable for use in absorbance measurement.
REAGENT PREPARATION
Bring all reagents to room temperature before use.
1 Wash Buffer If crystals have formed in the concentrate, warm up to room temperature a-n-d mix gently until the crystals have compley dissolved. Dilute 20 ml of Wash Buffer Concentrate into deionized or distilled water to prepare 500 ml of Wash Buffer.
2 Sta-n-dard Centrifuge the sta-n-dard vial at 6000-10000rpm for 30s. Reconstitute the Sta-n-dard with 1.0 ml of Sample Diluent. This reconstitution produces a stock solution of 1000 pg/ml. Allow the sta-n-dard to sit for a minimum of 15 minutes with gentle agitation prior to making serial dilutions. The undiluted sta-n-dard serves as the high sta-n-dard (1000 pg/ml). The Sample Diluent serves as the zero sta-n-dard (0 pg/ml). Prepare fresh for each assay. Use within 4 hours a-n-d discard after use.
3 Biotin-antibody Centrifuge the vial before opening. Dilute to the working concentration using Biotin-antibody Diluent(1:100), respectively.
4 HRP-avidin Centrifuge the vial before opening. Dilute to the working concentration using HRP-avidin Diluent(1:100), respectively.
Precaution: The Stop Solution provided with this kit is an acid solution. Wear eye, ha-n-d, face, a-n-d clothing protection when using this material.
OTHER SUPPLIES REQUIRED
1 Microplate reader capable of measuring absorbance at 450 nm, with the correction wavelength set at 540 nm or 570 nm.
2 Pipettes a-n-d pipette tips.
3 Deionized or distilled water.
4 Squirt bottle, manifold dispenser, or automated microplate washer.
5 An incubator which can provide stable incubation conditions up to 37°C±0.5°C.
SAMPLE COLLECTION A-N-D STORAGE
Serum Use a serum separator tube (SST) a-n-d allow samples to clot for 30 minutes before centrifugation for 15 minutes at 1000 g. Remove serum a-n-d assay immediay or aliquot a-n-d store samples at -20°C. Centrifuge the sample again after thawing before the assay. Avoid repeated freeze-thaw cycles.
Plasma Collect plasma using citrate, EDTA, or heparin as an anticoagulant. Centrifuge for 15 minutes at 1000 g within 30 minutes of collection. Assay immediay or aliquot a-n-d store samples at -20°C. Centrifuge the sample again after thawing before the assay. Avoid repeated freeze-thaw cycles.
Note: Grossly hemolyzed samples are not suitable for use in this assay.
ASSAY PROCEDURE
Bring all reagents a-n-d samples to room temperature before use. It is recommended that all samples, sta-n-dards, a-n-d controls be assayed in duplicate. All the reagents should be added directly to the liquid level in the well. The pipette should avoid contacting the inner wall of the well.
1 Add 100μl of Sta-n-dard, Blank, or Sample per well. Cover with the adhesive strip. Incubate for 2 hours at 37°C.
2 Remove the liquid of each well, don’t wash.
3 Add 100μl of Biotin-antibody working solution to each well. Incubate for 1 hour at 37°C. Biotin-antibody working solution may appear cloudy. Warm up to room temperature a-n-d mix gently until solution appears uniform.
4 Aspirate each well a-n-d wash, repeating the process three times for a total of three washes. Wash: Fill each well with
Wash Buffer (200μl) a-n-d let it sta-n-d for 2 minutes, then
remove the liquid by flicking the plate over a sink. The remaining drops are removed by patting the plate on a paper towel. Complete removal of liquid at each step is essential to good performance.
1 Add 100μl of HRP-avidin working solution to each well. Cover the microtiter plate with a new adhesive strip. Incubate for 1 hour at 37°C.
2 Repeat the aspiration a-n-d wash five times as step 4.
3 Add 90μl of TMB Substrate to each well. Incubate for 10-30
minutes at 37°C. Keeping the plate away from drafts a-n-d
other temperature fluctuations in the dark.
8. Add 50μl of Stop Solution to each well when the first four
wells containing the highest concentration of sta-n-dards
develop obvious blue color. If color change does not appear
uniform, gently tap the plate to ensure thorough mixing.
9. Determine the optical density of each well within 30 minutes,
using a microplate reader set to 450 nm.
CALCULATION OF RESULTS
Using the professional soft "Curve Exert 1.3" to make a sta-n-dard curve is recommended, which can be downloaded from our web.
Average the duplicate readings for each sta-n-dard, control, a-n-d sample a-n-d subtract the average zero sta-n-dard optical density. Create a sta-n-dard curve by reducing the data using computer software capable of generating a four parameter logistic (4-PL) curve-fit. As an alternative, construct a sta-n-dard curve by plotting the mean absorbance for each sta-n-dard on the x-axis against the concentration on the y-axis a-n-d draw a best fit curve through the points on the graph. The data may be linearized by plotting the log of the CCK concentrations versus the log of the O.D. a-n-d the best fit line can be determined by regression analysis. This procedure will produce an adequate but less precise fit of the data. If samples have been diluted, the concentration read from the sta-n-dard curve must be multiplied by the dilution factor.
LIMITATIONS OF THE PROCEDURE
1 The kit should not be used beyond the expiration date on the kit label.
2 Do not mix or substitute reagents with those from other lots or sources.
3 It is important that the Sta-n-dard Diluent selected for the sta-n-dard curve be consistent with the samples being assayed.
4 If samples generate values higher than the highest sta-n-dard, dilute the samples with the appropriate Sta-n-dard Diluent a-n-d repeat the assay.
5 Any variation in Sta-n-dard Diluent, operator, pipetting technique, washing technique, incubation time or temperature, a-n-d kit age can cause variation in binding.
6 This assay is designed to eliminate interference by soluble receptors, binding proteins, a-n-d other factors present in biological samples. Until all factors have been tested in the Immunoassay, the possibility of interference cannot be excluded.
TECHNICAL HINTS
1 Centrifuge vials before opening to collect contents.
2 When mixing or reconstituting protein solutions, always avoid foaming.
3 To avoid cross-contamination, change pipette tips between additions of each sta-n-dard level, between sample additions, a-n-d between reagent additions. Also, use separate reservoirs for each reagent.
4 When using an automated plate washer, adding a 30 second soak period following the addition of wash buffer, a-n-d/or rotating the plate 180 degrees between wash steps may improve assay precision.
5 To ensure accurate results, proper adhesion of plate sealers during incubation steps is necessary.
6 Substrate Solution should remain colorless or light blue until added to the plate. Keep Substrate Solution protected from light. Substrate Solution should change from colorless or light blue to gradations of blue.
7 Stop Solution should be added to the plate in the same order as the Substrate Solution. The color developed in the wells will turn from blue to yellow upon addition of the Stop Solution. Wells that are green in color indicate that the Stop Solution has not mixed thoroughly with the Substrate Solution.
