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

Executive Summary: Amiloride (MK-870) is a small-molecule inhibitor of epithelial sodium channels (ENaC) and urokinase-type plasminogen activator receptors (uPAR). It is widely employed in scientific research to dissect sodium channel function and receptor-mediated signaling pathways (APExBIO). The compound has a molecular weight of 229.63 and formula C6H8ClN7O, is supplied as a solid, and requires -20°C storage for stability. Amiloride acts as a PC2 channel blocker, modulating ion transport and cellular uptake mechanisms (Wang et al., 2018). Its use is restricted to research applications and is not suitable for diagnostic or therapeutic use.

Biological Rationale

Amiloride (MK-870) is central to studies of epithelial sodium channel (ENaC) activity. ENaC is a critical regulator of sodium ion (Na⁺) absorption in epithelial tissues, such as kidney, lung, and colon (APExBIO). Dysfunction of ENaC-mediated sodium transport is implicated in diseases including cystic fibrosis and hypertension (Related article). Amiloride also serves as an inhibitor of urokinase-type plasminogen activator receptors (uPAR), providing a tool to study cell signaling and migration. The compound’s action as a PC2 channel blocker expands its utility to broader ion channel research and cellular uptake mechanisms.

Mechanism of Action of Amiloride (MK-870)

Amiloride (MK-870) inhibits ENaC by competitively blocking the sodium ion pore, thus reducing sodium influx across epithelial membranes (Wang et al., 2018). The inhibition is reversible and concentration-dependent. In addition to ENaC, Amiloride binds to uPAR, interfering with receptor-mediated plasminogen activation and downstream signaling. The compound also blocks PC2 channels, influencing calcium and sodium signaling in various cell types. The molecular inhibition typically occurs at micromolar concentrations, and the effect is observed in vitro under standard physiological buffer and temperature (pH 7.4, 37°C).

Evidence & Benchmarks

• Amiloride blocks epithelial sodium channel (ENaC) activity in vitro, reducing Na⁺ absorption in cultured cells (Wang et al. 2018, https://doi.org/10.1186/s12985-018-0993-8).
• Amiloride does not inhibit clathrin-mediated endocytosis of type III grass carp reovirus, distinguishing its specificity for sodium channel and uPAR pathways (Wang et al. 2018, https://doi.org/10.1186/s12985-018-0993-8).
• Amiloride demonstrates stability as a solid at -20°C and should be used promptly after solution preparation to maintain activity (APExBIO).
• Inhibition of ENaC by Amiloride is dose-dependent, with IC₅₀ values typically in the low micromolar range under physiological conditions (referenced in related mechanistic article).

This article clarifies the distinct specificity of Amiloride for sodium channel and receptor inhibition, extending the mechanistic focus of this in-depth analysis article by directly benchmarking endocytic pathway assays (Wang et al. 2018). For expanded molecular insight into ENaC and uPAR inhibition, see this molecular perspective, which is complemented here by updated evidence on endocytosis limits.

Applications, Limits & Misconceptions

Amiloride (MK-870) is a standard tool for dissecting ENaC function, sodium channel research, and uPAR signaling studies. It is commonly applied in models of cystic fibrosis and hypertension to probe sodium transport mechanisms. The compound is also utilized for cellular endocytosis modulation, though recent evidence indicates its limitations in inhibiting some endocytic pathways (see below).

Common Pitfalls or Misconceptions

• Amiloride does not inhibit clathrin-mediated endocytosis of type III grass carp reovirus, despite utility in other endocytic assays (Wang et al., 2018).
• It is not a universal ion channel blocker, being selective for ENaC, uPAR, and PC2 channels only (related mechanistic article).
• Amiloride is not suitable for therapeutic or diagnostic use; it is for research only (APExBIO).
• Solutions of Amiloride are unstable over time; prolonged storage leads to loss of potency (APExBIO).
• Effectiveness can vary by experimental model and buffer composition; always validate concentration and conditions for each application.

Workflow Integration & Parameters

Amiloride (MK-870) is supplied by APExBIO as a solid reagent (SKU: BA2768). The molecular weight is 229.63 g/mol; chemical formula is C6H8ClN7O. Store at -20°C in a desiccated environment to maintain stability. Solutions should be prepared in DMSO or water and used immediately; avoid long-term storage of solutions due to degradation. Shipping conditions are Blue Ice for small molecules and Dry Ice for modified nucleotides. For ENaC inhibition assays, typical concentrations range from 1–100 μM, with IC₅₀ in the low micromolar range. Validation of inhibitory potency should be performed under physiological pH and temperature (pH 7.4, 37°C).

For more strategic guidance on workflow integration and competitive benchmarking, see the extended discussion in this strategic guide, which is updated here with direct reference to endocytic assay limitations and product stability data.

Conclusion & Outlook

Amiloride (MK-870) is a highly specific epithelial sodium channel and uPAR inhibitor, with robust application in sodium channel research, cellular uptake studies, and disease modeling for cystic fibrosis and hypertension. Recent evidence has delineated its mechanistic limits in endocytosis inhibition, emphasizing the need for careful experimental design. For detailed product specifications and research use, consult the official APExBIO product page. As mechanistic understanding advances, Amiloride (MK-870) will remain a cornerstone in the toolkit for ion channel and receptor pathway research.