Amiloride (MK-870): Epithelial Sodium Channel Inhibitor for Ion Channel and Endocytosis Research

Executive Summary: Amiloride (MK-870) is a potent inhibitor of epithelial sodium channels (ENaC) and urokinase-type plasminogen activator receptors (uPAR), used to interrogate ion channel function and cellular uptake pathways (APExBIO BA2768). Its selectivity and dual-action profile make it a standard in sodium channel and endocytosis assays (Wang et al., 2018). The compound is stable at -20°C and supplied as a solid (MW 229.63, C₆H₈ClN₇O), with rapid solution use recommended. Amiloride is widely applied in mechanistic research on cystic fibrosis, hypertension, and epithelial ion signaling. Its utility is bounded by pathways not mediated by ENaC or clathrin, as established in recent viral entry studies.

Biological Rationale

Ion channels regulate electrolyte balance, cell volume, and signaling in eukaryotic cells. The epithelial sodium channel (ENaC) is essential for sodium absorption in epithelial tissues, impacting fluid homeostasis and blood pressure (APExBIO). Dysregulation of ENaC is implicated in cystic fibrosis and hypertension research (see also), with Amiloride (MK-870) enabling targeted inhibition. Urokinase-type plasminogen activator receptor (uPAR) signaling intersects with pathways of cellular uptake and migration. By simultaneously inhibiting ENaC and uPAR, Amiloride provides a platform to dissect sodium transport, receptor-mediated endocytosis, and related signaling cascades. This duality distinguishes Amiloride from more selective ion channel blockers, offering versatility for mechanistic and translational research.

Mechanism of Action of Amiloride (MK-870)

Amiloride (MK-870) binds to and inhibits ENaC, preventing sodium influx across epithelial membranes. This inhibition occurs at sub-micromolar concentrations in vitro, with effects observable within minutes of compound application (Wang et al., 2018). Amiloride also antagonizes uPAR, influencing receptor-mediated endocytosis and cell migration. The compound can block PC2 (polycystin-2) channels, further modulating calcium and sodium signaling. Its mechanism is non-covalent and reversible, allowing for acute experimental manipulation. Amiloride’s broad inhibition profile enables assessment of both sodium transport and receptor uptake, but also necessitates careful experimental controls to delineate pathway specificity.

Evidence & Benchmarks

• Amiloride inhibits ENaC function, reducing sodium uptake in epithelial cells at concentrations of 1–100 μM (in vitro; see APExBIO).
• Amiloride (MK-870) does not block clathrin-mediated endocytosis of genotype III grass carp reovirus (GCRV104), confirming pathway specificity (Wang et al., 2018).
• Amiloride is effective as a PC2 channel blocker, impacting calcium and sodium flux in kidney-derived cells (internal review).
• In cystic fibrosis research, Amiloride reduces airway surface liquid absorption by inhibiting ENaC, supporting pathophysiological models (see use case).
• Amiloride is stable as a solid at -20°C; solutions should be freshly prepared and not stored long-term (APExBIO).

Applications, Limits & Misconceptions

Amiloride (MK-870) is routinely employed in sodium channel and endocytosis research. Its main applications include:

• Sodium channel research: Dissecting ENaC-mediated transport in epithelial and kidney cells.
• Cellular endocytosis modulation: Investigating receptor-mediated uptake by targeting uPAR and related pathways.
• Cystic fibrosis and hypertension models: Mimicking pathophysiological ENaC dysregulation in vitro.

This article extends prior guides (cf.) by providing explicit evidence boundaries and clarifying non-target pathways, such as clathrin-mediated viral entry, where Amiloride is ineffective.

Common Pitfalls or Misconceptions

• Amiloride does not inhibit clathrin-mediated endocytosis of all viruses; GCRV104 entry is unaffected (Wang et al., 2018).
• Amiloride is not suitable for pathways independent of ENaC or uPAR.
• Long-term storage of Amiloride solutions leads to degradation; always use freshly prepared aliquots (APExBIO).
• Amiloride is not a therapeutic or diagnostic agent; for research use only.
• Concentration and exposure time must be optimized for each assay; over-inhibition may produce off-target effects.

Workflow Integration & Parameters

For laboratory use, Amiloride (MK-870) is supplied as a solid and should be stored at -20°C. Solutions are prepared in sterile water or DMSO, filtered, and used immediately. Recommended working concentrations range from 1–100 μM, depending on assay and cell type. For ion channel assays, pre-incubation of 10–20 min at 37°C is typical. Shipping is under Blue Ice for small molecules; Dry Ice is used for nucleotides. Amiloride is compatible with patch clamp, electrophysiology, and cell viability assays. For detailed troubleshooting and protocol optimization, see this scenario-based guide, which contrasts practical solutions to common assay challenges addressed here by providing updated evidence boundaries.

Conclusion & Outlook

Amiloride (MK-870) from APExBIO remains a gold-standard tool for researchers probing epithelial sodium channels and uPAR-mediated cellular pathways. Its robust inhibition profile, ease of integration, and well-established safety for research make it essential for studies in cystic fibrosis, hypertension, and epithelial cell biology. However, pathway selectivity and storage constraints must be respected. For a strategic overview of future research directions, including competitive benchmarking and mechanistic insight, see this translational summary, which this article updates by providing the most recent peer-reviewed evidence on pathway specificity.

For product specifications, ordering, and technical data, visit the Amiloride (MK-870) product page (BA2768).