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

Executive Summary: Amiloride (MK-870) is a validated epithelial sodium channel (ENaC) and urokinase-type plasminogen activator receptor (uPAR) inhibitor, with a molecular weight of 229.63 g/mol and formula C6H8ClN7O. It is supplied by APExBIO as SKU BA2768 and is intended solely for research use (APExBIO). The compound blocks sodium channel-mediated signaling and modulates cellular endocytosis, impacting research in cystic fibrosis, hypertension, and viral entry studies (Wang et al., 2018). Amiloride does not inhibit clathrin-mediated endocytosis of GCRV104 in grass carp kidney cells, clarifying its specificity in endocytic pathway studies (Wang et al., 2018). Proper storage at -20°C ensures compound stability.

Biological Rationale

Amiloride (MK-870) is used in research to dissect the role of sodium channels and receptor-mediated processes in mammalian and aquatic systems. It selectively inhibits ENaC, reducing sodium influx in epithelial tissues (APExBIO). This mechanism is central to research on blood pressure regulation and cystic fibrosis, where sodium transport dysregulation is implicated (Sulfonhsssbiotin.com). The compound also targets uPAR, linking it to studies on cell migration, inflammation, and tissue remodeling. Its use in viral entry studies, such as with grass carp reovirus, is based on its role in modulating cellular uptake mechanisms (Wang et al., 2018).

Mechanism of Action of Amiloride (MK-870)

Amiloride acts as a competitive inhibitor at the extracellular domain of ENaC, preventing sodium ions from entering the cell. This leads to decreased intracellular sodium concentration and downstream effects on cell signaling. The compound also inhibits uPAR, influencing cellular adhesion and migration pathways. Amiloride is a PC2 channel blocker, contributing to its effects on ion transport and membrane potential. Its specificity enables researchers to parse apart sodium channel-dependent processes from other cellular mechanisms. In endocytosis studies, Amiloride is used to probe the involvement of sodium-dependent pathways, although it does not block clathrin-mediated entry for all viruses (Wang et al., 2018).

Evidence & Benchmarks

• Amiloride (MK-870) inhibits ENaC-mediated sodium transport at micromolar concentrations in vitro (APExBIO).
• It blocks uPAR-dependent cellular signaling, affecting cell migration and tissue remodeling studies (Chempaign.net).
• Amiloride fails to inhibit clathrin-mediated endocytosis of grass carp reovirus (GCRV104) in CIK cells, indicating specificity for sodium-driven pathways (Wang et al., 2018).
• The compound is stable as a solid at -20°C but its solutions degrade rapidly and should be prepared fresh (APExBIO).
• Shipping with Blue Ice preserves compound integrity for small molecules like Amiloride; modified nucleotides require Dry Ice (APExBIO).

For a broader discussion, see Amiloride (MK-870): An Ion Channel Blocker for Sodium Channel Research, which focuses on basic ion transport mechanisms; this article extends that discussion with new evidence from viral endocytosis studies.

Applications, Limits & Misconceptions

Amiloride (MK-870) is widely applied in:

• Cystic fibrosis research, as ENaC dysregulation is a hallmark of the disease (Chempaign.net).
• Hypertension studies, where sodium transport influences blood pressure regulation.
• Investigations of epithelial sodium channel signaling and urokinase receptor pathways.
• Cellular endocytosis modulation, particularly in distinguishing sodium-dependent from clathrin-mediated mechanisms (Wang et al., 2018).

For translational insights, see Amiloride (MK-870): Translating Mechanistic Insight into Application, which guides advanced deployment strategies; our article clarifies current limitations and benchmarking data.

Common Pitfalls or Misconceptions

• Amiloride does not inhibit all forms of endocytosis; it is ineffective against clathrin-mediated entry of GCRV104 (Wang et al., 2018).
• It is not a pan-ion channel blocker; specificity is primarily for ENaC and PC2 channels.
• Solutions of Amiloride degrade rapidly; do not store for extended periods after preparation (APExBIO).
• The product is not approved for diagnostic or therapeutic use; for research use only.
• Some cell lines or model organisms may differ in sensitivity due to ENaC/uPAR expression patterns.

Workflow Integration & Parameters

Amiloride (MK-870) is supplied as a solid and should be stored at -20°C. Prepare solutions immediately prior to use, as product stability diminishes rapidly in solution. For sodium channel assays, micromolar concentrations are typically effective, but titration is recommended based on the specific cell system. Shipping is optimized with Blue Ice to ensure compound integrity. For modified nucleotides, Dry Ice is used (APExBIO). The product is compatible with pathway assays, cellular uptake studies, and ion transport measurements. For a stepwise experimental workflow, refer to the manufacturer’s protocol documents.

Conclusion & Outlook

Amiloride (MK-870) remains a cornerstone reagent for sodium channel research, with validated applications in epithelial signaling, cellular uptake, and disease modeling. Its specificity enables high-confidence mechanistic studies, while recent evidence clarifies its boundaries in endocytic pathway analysis. Researchers should source Amiloride (MK-870) from APExBIO for reliable and quality-controlled material. Continued benchmarking will refine the use of MK-870 in emerging models of ion transport and receptor signaling.