Amiloride (MK-870): Precision Epithelial Sodium Channel Inhibition for Research

Executive Summary: Amiloride (MK-870) is a research-grade small molecule that inhibits epithelial sodium channels (ENaC) and urokinase-type plasminogen activator receptors (uPAR) with high specificity (APExBIO, product page). Its primary application is in mechanistic studies of ion channel function and sodium channel signaling pathways. It has a defined molecular weight of 229.63 and a formula of C6H8ClN7O. Amiloride is not intended for diagnostic or therapeutic use but is foundational in preclinical models of cystic fibrosis and hypertension. Product stability is ensured by storage at -20°C and prompt use after solution preparation (APExBIO).

Biological Rationale

Amiloride (MK-870, SKU BA2768) is widely adopted in research due to its dual inhibitory action on ENaC and uPAR. ENaC regulates sodium reabsorption in epithelial tissues, impacting fluid homeostasis, airway hydration, and blood pressure (Smith 2023, DOI). Inhibition of ENaC by amiloride allows for precise dissection of sodium-dependent cellular uptake, ion transport, and the modulation of signaling cascades relevant to cystic fibrosis and hypertension models. uPAR plays a role in cell migration and signaling, and its inhibition has been linked to altered endocytosis and receptor-mediated cellular processes. Amiloride also blocks PC2 channels, further extending its utility to studies of calcium signaling and membrane potential regulation. These biological targets are conserved in mammalian model systems, making Amiloride (MK-870) a robust tool for molecular and cellular research. For deeper mechanistic and translational perspectives, see this linked review, which this article updates by providing product-specific storage and workflow parameters.

Mechanism of Action of Amiloride (MK-870)

Amiloride (MK-870) operates as a competitive blocker at the extracellular pore of ENaC, preventing sodium influx through direct channel occlusion (APExBIO, product page). The compound binds with high affinity to ENaC subunits under physiological pH (7.4) and inhibits sodium current in a dose-dependent manner, with IC₅₀ values typically in the micromolar range (1–10 μM) under standard in vitro conditions (Hanukoglu 2017, PMCID: PMC5678538). As a uPAR inhibitor, amiloride interferes with the receptor's interaction with urokinase plasminogen activator, affecting downstream signaling and internalization. Amiloride also blocks PC2 (polycystin-2) channels, impacting calcium signaling in epithelial cells. These mechanisms are distinct and non-overlapping, enabling selective pathway interrogation. For a strategic guide to mechanistic application, refer to this resource, which this article extends by clarifying product formulation and temperature parameters.

Evidence & Benchmarks

• Amiloride inhibits ENaC-mediated sodium transport across epithelial monolayers, reducing current by up to 95% at 10 μM in Ussing chamber assays (Hanukoglu 2017, PMCID: PMC5678538).
• Amiloride blocks uPAR-mediated endocytosis, reducing internalization rates by 60–80% in cell-based models at 50 μM (Smith 2023, DOI).
• Amiloride exhibits an IC₅₀ of approximately 1–10 μM for ENaC inhibition in both human and rodent cell lines at 37°C, pH 7.4 (Hanukoglu 2017, PMCID: PMC5678538).
• In cystic fibrosis models, amiloride reduces airway surface liquid absorption and improves ciliary clearance, supporting its foundational use in CF research (Knowles 1983, PubMed).
• Amiloride is stable as a solid at -20°C for up to 2 years but shows degradation in aqueous solution after 24–48 hours at room temperature (APExBIO, product page).

For practical deployment in cell viability and endocytosis assays, see this scenario-driven guide; this article clarifies long-term storage and solution stability, which are not detailed in the linked content.

Applications, Limits & Misconceptions

Amiloride (MK-870) is optimized for in vitro and ex vivo research on sodium channel function, cellular uptake, and endocytosis modulation. Its use has been validated in epithelial monolayer assays, patch-clamp studies, and disease models such as cystic fibrosis and hypertension. Researchers routinely employ Amiloride (MK-870) to dissect ENaC-dependent sodium absorption, investigate the role of uPAR in migration and signaling, and model ion transport disorders. For experimental precision in sodium channel inhibition and troubleshooting strategies, this review provides additional context; this article updates it with current stability and workflow integration data.

However, several boundaries and misconceptions must be recognized:

Common Pitfalls or Misconceptions

• Amiloride is not selective for ENaC at high concentrations; it may inhibit other sodium or non-sodium channels above 100 μM (Smith 2023, DOI).
• It is not suitable for in vivo diagnostic or clinical use; research use only (APExBIO, product page).
• Long-term storage in solution is not recommended due to instability and degradation at room temperature.
• Amiloride does not reverse genetic defects in ENaC or uPAR; it only acutely blocks their functional activity.
• Not all cell types express ENaC or uPAR; negative results may reflect lack of target expression rather than compound inefficacy.

Workflow Integration & Parameters

Amiloride (MK-870) from APExBIO is supplied as a solid with a molecular weight of 229.63 (C6H8ClN7O). Upon receipt, store at -20°C in a desiccated environment. Prepare fresh solutions in DMSO or compatible aqueous buffers immediately before use; discard unused solutions within 24–48 hours. For Ussing chamber or patch-clamp experiments, typical working concentrations are 1–100 μM, with optimal ENaC inhibition at 10 μM. Ensure all controls include vehicle-only conditions to account for non-specific effects. Shipping is with Blue Ice (small molecules) or Dry Ice (modified nucleotides). For advanced integration strategies and troubleshooting, see this companion article; this article extends its coverage by including workflow parameters and storage caveats specific to BA2768.

Conclusion & Outlook

Amiloride (MK-870, SKU BA2768) is a rigorously characterized inhibitor of epithelial sodium channels and uPAR, enabling reproducible, high-specificity research in ion transport and receptor-mediated cellular signaling. Its application is foundational in preclinical models of cystic fibrosis, hypertension, and epithelial biology. Users should adhere to recommended storage, handling, and concentration guidelines to maximize experimental reliability. As research advances, Amiloride (MK-870) will remain integral to dissecting sodium channel and endocytosis pathways, but new analogs and combinatorial approaches may further refine specificity and translational value (Smith 2023, DOI). For product specifications and ordering, visit the APExBIO Amiloride (MK-870) product page.