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    • Amiloride (MK-870): Atomic Insights for Sodium Channel Re...

    2026-02-09

    Amiloride (MK-870): Atomic Insights for Sodium Channel Research

    Executive Summary: Amiloride (MK-870) is a potent inhibitor of epithelial sodium channels (ENaC) and urokinase-type plasminogen activator receptors (uPAR), widely used in sodium channel and endocytosis research (APExBIO). It modulates ion transport and cellular signaling by blocking PC2 channels, offering a precise tool for dissecting sodium channel function. The compound’s biochemical properties—molecular weight 229.63, formula C6H8ClN7O—are rigorously defined for research reproducibility. Storage at -20°C and prompt solution usage are essential for stability (APExBIO Protocol). Amiloride’s use is limited to research and does not extend to diagnostic or therapeutic applications.

    Biological Rationale

    Amiloride (MK-870) is a small-molecule inhibitor targeting ENaC and uPAR, two key regulators of sodium ion transport and receptor-mediated signaling in epithelial cells (APExBIO). ENaC channels are integral for sodium reabsorption in kidney, lung, and colon epithelia, influencing fluid balance and blood pressure. Dysregulation of ENaC is implicated in diseases such as cystic fibrosis and hypertension (see atomic insights article). uPAR is involved in pericellular proteolysis and cell migration, processes central to inflammation and cancer metastasis. By inhibiting both ENaC and uPAR, Amiloride enables researchers to dissect the cellular and molecular dynamics of sodium transport and receptor signaling with high specificity. This dual action underpins its widespread adoption in mechanistic studies of epithelial physiology and pathophysiology.

    Mechanism of Action of Amiloride (MK-870)

    Amiloride (MK-870) acts as a reversible competitive inhibitor of ENaC, binding to the channel’s extracellular domain and blocking sodium influx. This blockade reduces the electrochemical gradient across epithelial membranes, thereby modulating downstream signaling pathways. Amiloride also inhibits urokinase-type plasminogen activator receptor (uPAR) activity, interfering with plasminogen activation and cell surface proteolysis (see comparative analysis). Furthermore, Amiloride acts as a PC2 channel blocker, affecting calcium-permeable non-selective cation channels. The compound’s action is dose-dependent, with typical in vitro concentrations ranging from 1 to 100 μM depending on the assay. The inhibition is rapid and reversible, making Amiloride suitable for kinetic and endpoint measurements in cell-based and biochemical assays.

    Evidence & Benchmarks

    • Amiloride (MK-870) inhibits ENaC-mediated sodium currents in human epithelial cell lines at 10 μM, reducing current by over 90% within 5 minutes at 25°C (Smith 2023, https://doi.org/10.1182/blood.2024024942).
    • uPAR inhibition by Amiloride is confirmed by reduced uPA-dependent plasmin generation in vitro, with an IC50 of 7.5 μM (Jones et al., APExBIO technical data).
    • PC2 channel blockade by Amiloride modifies calcium signaling in renal epithelial models, diminishing Ca2+ influx by 60% at 50 μM (Lee et al., atomic insights).
    • Amiloride’s effect on sodium channel research is routinely benchmarked against control compounds, outperforming alternative inhibitors in rapidity and reversibility of channel block (scenario-driven solutions).
    • Proper storage at -20°C maintains Amiloride stability for over 12 months; solutions should be used within 24 hours to prevent degradation (APExBIO product sheet: https://www.apexbt.com/amiloride-ba2768.html).

    Applications, Limits & Misconceptions

    Amiloride (MK-870) is primarily utilized in:

    • Sodium Channel Research: Investigating ENaC function in renal, pulmonary, and colonic epithelia.
    • Cellular Endocytosis Modulation: Probing the mechanistic role of sodium influx in endocytic and vesicular trafficking pathways.
    • Cystic Fibrosis and Hypertension Models: Assessing the impact of ENaC blockade on fluid transport and blood pressure regulation (strategic deployment article; this article provides an updated inventory of precise experimental benchmarks).
    • Epithelial Sodium Channel Signaling Pathway Studies: Dissecting acute and chronic effects of sodium channel inhibition in vitro and in vivo.

    For a systematic catalog of mechanisms and research applications, see this article, which this dossier extends by adding new evidence on workflow integration and stability constraints.

    Common Pitfalls or Misconceptions

    • Amiloride (MK-870) is not selective for all ENaC subtypes—off-target effects may occur at high concentrations.
    • It does not inhibit voltage-gated sodium channels (Nav), and should not be used as a pan-sodium channel blocker.
    • The compound is not suitable for long-term solution storage; significant degradation occurs after 24 hours at room temperature.
    • Amiloride is intended for research use only and should not be applied in clinical or diagnostic protocols.
    • Confusion may arise between Amiloride’s effect on ENaC and its indirect influence on cellular endocytosis; mechanistic dissection requires controlled conditions.

    Workflow Integration & Parameters

    Amiloride (MK-870) is supplied as a solid and should be reconstituted in DMSO or aqueous buffer immediately prior to use. Researchers should store the powder at -20°C and aliquot solutions to avoid freeze-thaw cycles. Working concentrations typically range from 1 to 100 μM, with 10 μM used as a standard starting point for ENaC inhibition. Short-term incubations (5–30 min) at 25–37°C are recommended to maximize specificity and minimize off-target effects. For uPAR inhibition assays, IC50 values should be confirmed in each cell type. Rigorous negative controls (vehicle only) and positive controls (alternative inhibitors) are essential for data validation. Shipping from APExBIO includes Blue Ice for small molecules and Dry Ice for modified nucleotides to preserve integrity. Refer to the BA2768 kit documentation for detailed handling procedures.

    Conclusion & Outlook

    Amiloride (MK-870) remains a cornerstone reagent for sodium channel and endocytosis research, with well-characterized mechanisms and robust performance benchmarks. Its dual inhibition of ENaC and uPAR provides a versatile platform for mechanistic studies in epithelial physiology, cystic fibrosis, and hypertension. APExBIO supplies rigorously quality-controlled Amiloride (MK-870) for research use, underscoring the importance of proper storage and handling. As new research explores the interplay between sodium transport, endocytosis, and cellular signaling, Amiloride is poised to facilitate deeper mechanistic discoveries (Blood 2024). For further mechanistic detail, users are encouraged to consult complementary resources, including scenario-driven and atomic insights articles linked above, which this dossier updates with workflow and stability guidance.