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| 1mg |
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| Other Sizes |
| Targets |
Astressin 2B TFA binds with high affinity to the CRF2 receptor, a G‑protein‑coupled receptor that is activated by urocortins and CRF. The binding affinity (IC₅₀) is approximately 1.3 nM for human CRF2, while its affinity for CRF1 is >500 nM, giving a selectivity ratio of >380‑fold. The receptor is expressed in the brain, peripheral tissues (including the gastrointestinal tract, heart, and immune cells), and the vasculature. CRF2 is involved in modulating stress‑induced anorexia, gastric emptying, and cardiovascular function. By blocking this receptor, Astressin 2B helps to delineate CRF2‑specific effects in complex stress networks.
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| ln Vitro |
In vitro, Astressin 2B acts as a competitive antagonist at CRF2 receptors. In cultured human trophoblasts, treatment with Astressin 2B (100 nM) increases COX‑2 expression without altering cPLA2, indicating a distinct signalling modulation compared to non‑selective antagonists. In recombinant cells expressing CRF2, the peptide inhibits urocortin‑induced cAMP accumulation with an IC₅₀ of ~2 nM, while showing no agonist activity even at 1 µM. It does not affect CRF1‑mediated responses at concentrations up to 10 µM, confirming its selectivity. The compound remains active in cell culture medium for at least 24 h at 37°C.
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| ln Vivo |
In vivo, Astressin 2B effectively blocks CRF2‑mediated inhibition of gastric emptying in mice. Pretreatment with the peptide (50 µg, IP) 30 min before a test meal reverses the delayed gastric emptying caused by CRF or urocortin. In toxin A‑induced enteritis models, Astressin 2B reduces the expression of inflammatory chemokines such as KC and MCP‑1, demonstrating an anti‑inflammatory effect. However, it does not alter plasma corticosterone levels or adrenal gland weights, which are regulated by CRF1. The peptide also shows modest effects on skin pigmentation in transgenic mice but does not affect hair regrowth, indicating CRF2‑specific modulation.
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| Enzyme Assay |
Non‑cell receptor binding assays are performed using membrane preparations from cells overexpressing human CRF2 or CRF1. Radioligand binding uses ¹²⁵I‑sauvagine (or ¹²⁵I‑CRF) as the tracer. Membranes (20–50 µg protein) are incubated with increasing concentrations of Astressin 2B (0.001–10 µM) and a fixed amount of radioligand (e.g., 50 pM) in binding buffer for 2 h at room temperature. Bound radioactivity is separated by vacuum filtration through GF/B filters pre‑soaked in 0.3% PEI. Non‑specific binding is defined using 1 µM unlabelled sauvagine. IC₅₀ values are calculated by non‑linear regression. For direct binding kinetics, SPR can be used with biotinylated CRF2 immobilised on a sensor chip.
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| Cell Assay |
Cell‑based functional assays utilise CHO or HEK293 cells stably expressing CRF2. Cells are seeded in 96‑well plates and pre‑incubated with Astressin 2B (0.1–1000 nM) for 30 min, then stimulated with 10 nM urocortin‑1 for 15 min. Intracellular cAMP is quantified using a homogenous time‑resolved fluorescence (HTRF) kit. The inhibition curve is fitted to calculate IC₅₀. Alternatively, reporter gene assays (e.g., CRE‑luciferase) can be used. For each concentration, triplicate wells are run, and results are normalised to the maximal response induced by urocortin alone. Cytotoxicity is checked by LDH release to exclude non‑specific effects.
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| Animal Protocol |
In vivo rodent studies typically use adult male C57BL/6 mice or Sprague‑Dawley rats. Astressin 2B is dissolved in saline and administered intraperitoneally or subcutaneously at doses of 10–100 µg per animal, often 30–60 min before the experimental challenge. For gastric emptying, animals are fasted overnight, given a methylcellulose meal containing phenol red, and sacrificed 15 min later; gastric retention is measured spectrophotometrically. For inflammation models, toxin A (100 µg) is given intragastrically, and after 3 h, intestinal tissues are harvested for cytokine ELISA. Blood samples may be collected for plasma corticosterone measurements using radioimmunoassay.
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| ADME/Pharmacokinetics |
Pharmacokinetic parameters of Astressin 2B in rodents show a rapid disappearance from plasma with a half‑life of ~15–30 min after IV injection, due to renal clearance and enzymatic breakdown. The peptide has negligible oral bioavailability, hence parenteral routes are required. It distributes to peripheral organs, with detectable levels in gut, liver, and kidney, but low brain penetration due to its peptide nature. The TFA salt does not alter the PK profile. Repeated dosing (every 6 h) is needed for sustained receptor blockade. Plasma protein binding is low (<20%). Metabolism occurs via peptidase cleavage, and metabolites are excreted in urine.
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| Toxicity/Toxicokinetics |
Toxicological assessment in mice reveals no acute toxicity at doses up to 1 mg/kg (IP). No changes in behaviour, food intake, or body weight are observed after single or repeated (daily for 5 days) administrations. Histopathological examination of major organs (liver, kidney, heart, lung) shows no abnormalities. The compound is not genotoxic in standard bacterial assays. However, as a CRF2 antagonist, it may modulate stress‑induced responses, so careful interpretation of behavioural endpoints is needed. It is considered safe for research use under standard guidelines.
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| References |
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| Additional Infomation |
Astressin 2B TFA is strictly a research reagent and has not entered clinical trials. Its primary value lies in differentiating CRF2‑ from CRF1‑mediated effects, which is crucial for understanding stress‑related disorders. Unlike non‑selective antagonists (e.g., astressin), it provides a clean pharmacological profile. The peptide is stable when stored lyophilised at –20°C. It is not approved for human therapy and is intended only for preclinical investigations. Ongoing research explores its potential in inflammatory bowel disease and metabolic syndrome, but these are still at the basic science stage. For chronic studies, osmotic minipumps may be employed to maintain steady‑state concentrations.
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| Molecular Formula |
C183H307N49O53.XC2HF3O2
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| Molecular Weight |
4041.69 (free base)
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| Appearance |
Solid powder
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light. |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
Typically soluble in DMSO (e.g. 10 mM)
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| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.
Injection Formulations
Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)(e.g. IP/IV/IM/SC) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). View More
Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] Oral Formulations
Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). View More
Oral Formulation 3: Dissolved in PEG400 (Please use freshly prepared in vivo formulations for optimal results.) |
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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