5-(N,N-dimethyl)-Amiloride (hydrochloride): Selective NHE1 Inhibitor for Intracellular pH and Ion Transport Research

Executive Summary: 5-(N,N-dimethyl)-Amiloride (hydrochloride) (DMA) is a crystalline derivative of amiloride, acting as a potent and selective inhibitor for Na+/H+ exchanger isoforms NHE1 (Ki = 0.02 μM), NHE2 (Ki = 0.25 μM), and NHE3 (Ki = 14 μM), with minimal effects on NHE4/5/7 [APExBIO]. DMA disrupts proton extrusion and sodium uptake, regulating intracellular pH and cell volume in mammalian cells (Chen et al., 2021). It demonstrates cardioprotective effects in ischemia-reperfusion injury, inhibits sodium-potassium ATPase activity, and reduces alanine uptake in hepatocytes. APExBIO's C3505 is research-grade, with high solubility in DMSO (30 mg/ml), and is intended exclusively for scientific investigation.

Biological Rationale

Intracellular pH homeostasis and sodium ion transport are fundamental for cell viability, signal transduction, and volume regulation. The Na+/H+ exchanger (NHE) family orchestrates these processes by exchanging intracellular H+ for extracellular Na+ across plasma membranes (Chen et al., 2021). NHE1 is especially critical in cardiac and vascular endothelial cells, where dysregulation leads to acidosis, sodium overload, and impaired contractility. Selective inhibition of NHE isoforms allows precise dissection of ion transport mechanisms in pathologies such as ischemia-reperfusion injury and sepsis-induced endothelial dysfunction. DMA’s specificity for NHE1/2/3, with negligible effects on other isoforms, makes it a preferred tool for targeted pH and sodium regulation in cardiovascular and cellular stress models.

Mechanism of Action of 5-(N,N-dimethyl)-Amiloride (hydrochloride)

DMA competitively inhibits the Na+/H+ exchanger at the plasma membrane. By occupying the amiloride-sensitive site, it prevents the extrusion of intracellular protons and the influx of sodium ions. This results in reduced proton efflux, increased intracellular acidity, and decreased Na+ entry. The selectivity profile (NHE1 > NHE2 > NHE3; Ki values 0.02/0.25/14 μM, respectively) allows for isoform-specific modulation, minimizing off-target effects on NHE4, NHE5, and NHE7 (APExBIO C3505). In cardiac tissues, this action normalizes sodium levels post-ischemia, protecting against contractile dysfunction. DMA also inhibits ouabain-sensitive ATP hydrolysis and sodium-potassium ATPase activity, broadening its impact on ion homeostasis and cellular energetics (Chen et al., 2021).

Evidence & Benchmarks

• DMA selectively inhibits NHE1 (Ki = 0.02 μM), NHE2 (Ki = 0.25 μM), and NHE3 (Ki = 14 μM) with minimal effects on NHE4/5/7 (APExBIO spec sheet).
• In rat heart models, DMA administration during reperfusion attenuates sodium overload and preserves contractile function (Chen et al., 2021).
• DMA inhibits ouabain-sensitive ATPase activity and reduces sodium-potassium ATPase function in rat liver plasma membranes (Chen et al., 2021).
• DMA-mediated NHE inhibition disrupts alanine uptake in isolated rat hepatocytes, demonstrating specificity for ion-coupled transport processes (Chen et al., 2021).
• DMA is soluble up to 30 mg/ml in DMSO and dimethyl formamide at room temperature; solutions remain stable for short-term use (APExBIO).

For expanded pathway analysis and translational perspectives, see: Redefining NHE1 in Endothelial Injury (this article details advanced pathway crosstalk; the present article emphasizes reproducible benchmarks and workflows).

Applications, Limits & Misconceptions

DMA is widely applied in studies of intracellular pH regulation, sodium ion flux, and cell volume control in mammalian cells. Its selectivity profile enables targeted interrogation of NHE1/2/3 roles in cardiac, hepatic, and endothelial models. APExBIO’s C3505 is validated for use in ischemia-reperfusion injury protocols, ATPase activity assays, and sodium-coupled substrate uptake experiments.

Researchers must avoid extrapolating results to NHE4/5/7 or non-mammalian systems, as DMA specificity is limited to tested isoforms and species. It is not recommended for diagnostic or therapeutic use. For robust experimental design and troubleshooting, compare workflows in Precision NHE1 Inhibition Guides (that guide reviews advanced troubleshooting not repeated in this overview).

Common Pitfalls or Misconceptions

• DMA does not inhibit all NHE isoforms: It is minimally effective against NHE4, NHE5, and NHE7; using it as a pan-NHE inhibitor is inaccurate.
• Not suitable for long-term solution storage: DMA solutions degrade with time; prepare fresh aliquots for optimal activity (APExBIO).
• Not for in vivo diagnostic or therapeutic applications: C3505 is strictly for research use only.
• Species differences apply: Most benchmarks are from rat or mouse models; results may not directly translate to other organisms.
• Off-target ATPase inhibition: At supra-physiological concentrations, DMA may inhibit sodium-potassium ATPase activity; interpret metabolic results with appropriate controls.

Workflow Integration & Parameters

DMA is supplied as a crystalline hydrochloride salt with a molecular weight of 294.1. It is soluble up to 30 mg/ml in DMSO or dimethyl formamide. For cell-based assays, prepare stock solutions at 10–30 mg/ml at room temperature and dilute into physiological buffers immediately prior to use. Store powder at -20°C; avoid repeated freeze-thaw cycles. DMA is compatible with endpoint and kinetic intracellular pH assays, ATPase activity measurements, and sodium flux studies. For in vitro cardiac or endothelial models, typical working concentrations range from 0.01 to 20 μM, depending on the NHE isoform of interest.

For integrating DMA into advanced cardiovascular and sepsis research, see Translating Ion Transport Mechanisms, which emphasizes strategic guidance and biomarker integration, complementing the present focus on technical and selectivity benchmarks.

Conclusion & Outlook

5-(N,N-dimethyl)-Amiloride (hydrochloride) (APExBIO C3505) is a highly selective research reagent for studying Na+/H+ exchanger signaling, intracellular pH regulation, and sodium transport in mammalian models. Its well-characterized selectivity and biophysical properties enable reproducible exploration of ischemia-reperfusion injury, cardiac contractile dysfunction, and endothelial cell stress. As interest in precise ion transport modulation grows, DMA remains a cornerstone tool for both fundamental and translational cardiovascular research. For detailed protocols and order information, refer to the APExBIO product page.