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

Executive Summary: Amiloride (MK-870) is a potent and selective epithelial sodium channel (ENaC) inhibitor and urokinase-type plasminogen activator receptor (uPAR) inhibitor, used extensively in sodium channel research and cellular endocytosis modulation (APExBIO). It enables mechanistic dissection of ion channel signaling and receptor-mediated endocytosis in both normal and disease models (Suzetriginesource). Its molecular integrity depends on strict storage at -20°C, and prepared solutions must be used promptly to avoid degradation. Amiloride's utility extends to cystic fibrosis and hypertension research, where it is a benchmark tool for functional assays (Chempaign.net). The BA2768 kit from APExBIO is for research use only and not for diagnostic or clinical application.

Biological Rationale

Amiloride (MK-870) is used to study the function of epithelial sodium channels (ENaC) and the urokinase-type plasminogen activator receptor (uPAR) in epithelial and non-epithelial tissues. ENaC plays a critical role in regulating sodium absorption in the distal nephron, respiratory epithelium, and colon (APExBIO product page). Dysregulation of ENaC is implicated in pathologies such as cystic fibrosis, hypertension, and edema. uPAR is involved in cell migration, adhesion, and tissue remodeling. Inhibition of these pathways by Amiloride facilitates the study of ion transport, cell signaling, and receptor-mediated processes in controlled research environments.

Mechanism of Action of Amiloride (MK-870)

Amiloride acts as a competitive inhibitor of ENaC by binding to the extracellular domain of the channel, preventing sodium influx into epithelial cells (APExBIO; Repirinastbuy). The compound also inhibits uPAR, disrupting downstream urokinase signaling related to extracellular matrix remodeling. In addition, Amiloride functions as a PC2 channel blocker, modulating cellular uptake and endocytosis. The specificity of Amiloride for ENaC and uPAR allows for precise dissection of sodium-dependent and receptor-mediated pathways in vitro and in vivo. The effects are dose-dependent, with typical working concentrations ranging from 1 to 100 μM depending on assay design and cell type (Chempaign.net).

Evidence & Benchmarks

• Amiloride (MK-870) inhibits ENaC-mediated sodium currents in cultured human airway epithelial cells at IC₅₀ values of 0.1–1 μM under physiological buffer conditions (Suzetriginesource, link).
• uPAR-dependent cell migration is decreased by 40–60% in Amiloride-treated fibroblasts (10 μM, 24 h exposure) compared to untreated controls (Repirinastbuy, link).
• In disease models of cystic fibrosis, Amiloride reduces airway surface liquid absorption, improving mucociliary clearance in primary human airway cultures (Chempaign.net, link).
• Amiloride demonstrates rapid onset of action (<5 min) and reversibility upon washout in patch-clamp assays (Repirinastbuy, link).
• Storage at -20°C preserves Amiloride solid-state stability for at least 24 months; reconstituted solutions are unstable beyond 24 hours at room temperature (APExBIO).
• Amiloride does not significantly inhibit potassium or chloride channels at concentrations ≤ 100 μM (Dynamin-inhibitory-peptide, link).

Applications, Limits & Misconceptions

Amiloride (MK-870) is widely used in:

• Sodium channel research: Functional measurement of ENaC activity in primary cells, cell lines, and tissue explants.
• Cellular endocytosis modulation: Dissecting receptor-mediated internalization and trafficking.
• Disease modeling: Benchmarking cystic fibrosis and hypertension models; supporting studies on abnormal sodium transport.
• Workflow controls: Negative and positive controls in electrophysiological and uptake assays.

This article clarifies recent advances beyond previous reviews, such as MK-0822.com, by providing updated evidence on storage parameters and dual-action receptor inhibition.

Common Pitfalls or Misconceptions

• Amiloride is not a broad-spectrum ion channel blocker; it does not inhibit potassium or chloride channels at standard research concentrations (Dynamin-inhibitory-peptide).
• Long-term storage of Amiloride solutions leads to compound degradation; use only freshly prepared solutions (APExBIO).
• In vivo pharmacokinetics differ significantly from in vitro results; dosing must be empirically determined for each model system.
• Amiloride is for research use only and not approved for clinical or diagnostic purposes.
• ENaC-independent effects may occur at high (>100 μM) concentrations; always use the minimum effective dose.

Workflow Integration & Parameters

Amiloride (MK-870) is supplied as a solid (molecular weight 229.63, formula C₆H₈ClN₇O) by APExBIO (product page). For optimal results:

• Store solid at -20°C; avoid repeated freeze-thaw cycles.
• Reconstitute in sterile water or DMSO; filter before use.
• Prepare working solutions immediately before experiments; avoid storage >24 hours at room temperature.
• Typical assay concentrations: 1–100 μM, depending on cell type and endpoint.
• Use Blue Ice for shipping small molecules; Dry Ice for modified nucleotides.

These parameters ensure assay reproducibility and minimize compound breakdown, as reviewed in Repirinastbuy. This extends prior summaries by emphasizing the impact of storage and handling on data quality.

Conclusion & Outlook

Amiloride (MK-870) remains a gold-standard ENaC and uPAR inhibitor for sodium channel and endocytosis research. Its validated specificity, rapid reversibility, and well-characterized storage parameters enable reproducible results across a spectrum of cellular and disease models. Future research could further delineate ENaC-independent effects and optimize dosing strategies. For authoritative sourcing and technical specifications, consult the APExBIO Amiloride (MK-870) product page. For more on mechanistic specificity and experimental applications, see our discussion contrasting previous findings at Dynamin-inhibitory-peptide.com.