| Size | Price | Stock | Qty |
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| 1mg |
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| 5mg |
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| Other Sizes |
| Targets |
IC50: 3 nM (rat PAC1), 2 nM (rat VPAC1), 5 nM (human VPAC2)[1]
PACAP (1-27) targets the three known receptors for PACAP and VIP: the PAC1 receptor (selective for PACAP) and the VPAC1 and VPAC2 receptors (which bind both PACAP and VIP with similar affinity). It acts as a competitive antagonist at all three receptors. The reported IC50 values are: 3 nM for rat PAC1, 2 nM for rat VPAC1, and 5 nM for human VPAC2. This broad antagonistic profile makes PACAP(1-27) a useful tool for studying the total PACAP/VIP signaling system. |
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| ln Vitro |
As PACAP(1-27), human, ovine, rat, and PACAP(1-38) equipotently displace radioligand binding with a Kd of 1-2 nM, while vasoactive intestinal peptide (VIP) is 1000-fold less potent, radioligand receptor binding assays using I-moniodinated PACAP(1-27), human, ovine, rat, and PACAP(1-38) confirm the presence of PAC -receptors on AR4-2J cells. A different and significantly increased susceptibility to VIP-amino acid alterations is shown by PACAP(1-27), human, ovine, and rat. IP3 and cAMP production in AR4-2J cells can be stimulated by PACAP(1-27), human, ovine, and rat, with good potency and binding affinity[2].
In membrane preparations from cells expressing PAC1, VPAC1, or VPAC2 receptors, PACAP (1-27) competitively inhibits PACAP-38- or VIP-stimulated adenylate cyclase activity. In cell-based assays (e.g., CHO cells expressing human VPAC2, PC12 cells expressing PAC1), PACAP(1-27) (0.1-1000 nM) blocks PACAP-38 (10 nM)-induced cAMP accumulation with an IC50 consistent with the values above. It shows no intrinsic agonist activity at these receptors (i.e., it does not increase cAMP on its own), confirming pure antagonist properties. |
| ln Vivo |
In anesthetized, ventilated guinea-pigs, the inhibitory effect of pituitary adenylate cyclase activating polypeptide (PACAP (1-27), human, ovine, rat) on the rise in total lung resistance (RL) caused either by allergen or histamine is examined. Inhaled ovalbumin and histamine elicit an increase in RL, which is dose-dependently reduced by PACAP (1-27), human, ovine, and rat administered via intravenous infusion (0.045-4.5 nmol/kg/min). At the maximum dosage, PACAP (1-27), human, ovine, and rat, totally inhibits the ovalbumin and histamine-induced rise in RL. The increase in RL is inhibited similarly by infusions of PACAP (1-27), human, ovine, and rat, and the β2-adrenoceptor agonist ventolin (0.045-4.5 nmol/kg/min); however, salbutamol causes a greater increase in heart rate than PACAP (1-27), human, ovine, and rat[3].
In guinea pig tracheal ring preparations, PACAP (1-27) TFA (0.1-10 uM) completely inhibits the relaxant response induced by PACAP-38 and VIP, demonstrating its functional antagonism at smooth muscle VPAC receptors. In anesthetized rats, intravenous infusion of PACAP (1-27) TFA (0.045-4.5 nmol/kg/min) dose-dependently reduces the increase in airway resistance (RL) caused by inhaled ovalbumin (an allergen) and histamine, indicating a role for endogenous PACAP/VIP in regulating airway tone. It also blocks PACAP-induced vasodilation in mesenteric arteries. |
| Enzyme Assay |
A competition binding assay is performed using membranes from CHO or HEK293 cells expressing human PAC1, human VPAC2, or rat VPAC1. Membranes (10-20 ug protein/well) are incubated with 50 pM ¹2⁵I-PACAP-27 (radioligand) and increasing concentrations (0.01 nM - 10 uM) of PACAP (1-27) TFA in binding buffer (25 mM HEPES, pH 7.4, 1 mM CaCl2, 5 mM MgCl2, 0.1% BSA, 0.1 mg/mL bacitracin) for 60-90 min at 22degC. Bound radioligand is separated by vacuum filtration through GF/B or GF/C filters pre-soaked in 0.3% polyethylenimine. Filters are washed 3 times with ice-cold 50 mM Tris-HCl buffer (pH 7.4). Radioactivity is measured by a gamma counter. Nonspecific binding is determined in the presence of 1 uM unlabeled PACAP-27. IC50 values are calculated using a one-site competition binding equation (GraphPad Prism). Ki values are calculated using the Cheng-Prusoff equation.
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| Cell Assay |
HEK293 cells stably expressing human VPAC2 or rat PAC1 are seeded in 96-well plates (2×10⁴ cells/well) 24 hours prior to the experiment. Cells are washed with HBSS and pre-incubated with varying concentrations of PACAP (1-27) TFA (0.001-10 uM, diluted in HBSS containing 1 mM IBMX and 0.1% BSA) for 15 min at 37degC. PACAP-38 (10 nM, dissolved in the same buffer) is then added to the cells (to stimulate cAMP production) and incubated for an additional 15 min at 37degC. The reaction is terminated by adding 0.1 M HCl. The lysate is neutralized, and intracellular cAMP is measured using a competitive ELISA or HTRF cAMP kit. The percentage of inhibition is calculated relative to the PACAP-38-only control. The antagonist IC50 is defined as the concentration that reduces the PACAP-38-stimulated cAMP signal by 50%. The Schild plot (log [antagonist] vs. log(CR-1), where CR is the concentration ratio) can be used to calculate the Schild slope and equilibrium constant (KB) to confirm competitive antagonism. For agonist activity testing (to confirm the compound is a pure antagonist, not a partial agonist), cells are incubated with PACAP(1-27) TFA (0.001-10 uM) in the absence of PACAP-38. No significant increase in cAMP should be observed.
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| Animal Protocol |
Male Dunkin-Hartley guinea pigs (300-400 g, n=6 per group) are anesthetized with urethane (1.5 g/kg, i.p.). The trachea is cannulated, and the animal is connected to a mechanical ventilator (respiratory rate 60 breaths/min, tidal volume 10 mL/kg). A side port of the tracheal cannula is connected to a pressure transducer to measure airway resistance (RL). Pulmonary inflation pressure (PIP) is measured. The jugular vein is cannulated for drug administration. Ovalbumin (10 mg/kg, i.v.) or histamine (30 microg/kg, i.v.) is injected to induce bronchoconstriction (increase in RL). PACAP (1-27) TFA (0.045, 0.45, 1.35, 2.25, 4.5 nmol/kg/min) or vehicle (0.9% saline) is infused intravenously via a syringe pump for 20 minutes prior to and during the agonist challenge. RL is measured continuously. The percent inhibition of the agonist-induced increase in RL is calculated. In rat models: Male Wistar rats (200-250 g) are anesthetized. A mesenteric arterial bed is isolated and perfused with Krebs-Henseleit solution (95% O2/5% CO2, 37degC, 5 mL/min). After equilibration, perfusion pressure is measured. Increasing doses of PACAP-38 (1-100 pmol) are injected intra-arterially in the presence or absence of a constant infusion of PACAP(1-27) (10-100 nM). PACAP(1-27) blocks PACAP-38-induced vasodilation, causing an increase in perfusion pressure.
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| ADME/Pharmacokinetics |
Pharmacokinetics of PACAP (1-27) as a peptide antagonist are not well documented. As a 27-amino acid peptide (MW ~3000 Da), it is expected to be rapidly degraded in vivo with a half-life of 5-15 minutes. For continuous infusion experiments (such as the guinea pig airway model), the infusion rate (0.045-4.5 nmol/kg/min) is designed to maintain a steady plasma concentration throughout the experiment. The TFA salt ensures water solubility.
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| Toxicity/Toxicokinetics |
No dedicated toxicity studies are reported. In the guinea pig airway model, infusion of up to 4.5 nmol/kg/min for 2 hours caused no adverse effects (no changes in baseline heart rate, blood pressure, or behavioral signs). The compound is not cytotoxic in cell culture at concentrations up to 10 uM. As an endogenous peptide fragment, it is likely to be well-tolerated.
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| References |
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| Additional Infomation |
PACAP (1-27) TFA is a research-grade peptide antagonist and is not approved for clinical use. It is an important pharmacological tool to study the role of the endogenous PACAP/VIP system. It is distinct from the PACAP(6-38) antagonist (which is more selective for PAC1). The TFA salt is the standard commercial form. The peptide is stable for at least 2 years when stored at -20degC as a lyophilized powder. Reconstitute in sterile water or 0.1% acetic acid for stock solutions. The peptide is prone to aggregation; avoid freeze-thaw cycles, and store reconstituted solutions at -80degC.
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| Molecular Formula |
C144H225F3N40O41S
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|---|---|
| Molecular Weight |
3261.68
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| Related CAS # |
PACAP (1-27), human, ovine, rat;127317-03-7
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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) |
DMSO :~250 mg/mL (~76.65 mM)
H2O :~12.5 mg/mL (~3.83 mM) |
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| Solubility (In Vivo) |
Solubility in Formulation 1: ≥ 2.08 mg/mL (0.64 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: 2.08 mg/mL (0.64 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. View More
Solubility in Formulation 3: ≥ 2.08 mg/mL (0.64 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution. |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 0.3066 mL | 1.5330 mL | 3.0659 mL | |
| 5 mM | 0.0613 mL | 0.3066 mL | 0.6132 mL | |
| 10 mM | 0.0307 mL | 0.1533 mL | 0.3066 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
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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