What Is Demeclocycline Hydrochloride?

Demeclocycline hydrochloride (CAS 64-73-3) is the hydrochloride salt of demeclocycline, a naturally occurring tetracycline-class antibiotic originally derived from Streptomyces aureofaciens. It belongs to the polycyclic naphthacene carboxamide family of compounds and shares the characteristic four-ring core structure common to all tetracyclines.

In research settings, demeclocycline hydrochloride is primarily valued not as an antimicrobial agent but as a pharmacological tool compound. It is well established as an antagonist of antidiuretic hormone (ADH, also known as arginine vasopressin, AVP) at the level of the renal collecting duct. By interfering with ADH-mediated signaling—specifically by impairing cAMP generation and downstream aquaporin-2 (AQP2) trafficking—demeclocycline induces a state of nephrogenic diabetes insipidus, which makes it a useful in vitro and in vivo tool for SIADH-related research.

Mechanism of Action in Research Models

Demeclocycline hydrochloride exerts its ADH-antagonist effect primarily in renal collecting duct principal cells. Under normal physiology, ADH binds to vasopressin V2 receptors (V2R) on the basolateral membrane, activating adenylyl cyclase via Gs proteins to elevate intracellular cAMP. This cAMP signal activates protein kinase A (PKA), which phosphorylates AQP2 water channels and promotes their insertion into the apical membrane, increasing water reabsorption.

Demeclocycline disrupts this pathway at a post-receptor level, impairing cAMP accumulation and thereby reducing AQP2-mediated water permeability. The precise molecular target within the cAMP cascade has not been fully elucidated, and researchers should note that mechanistic details may vary across cell types and model systems. This functional antagonism of ADH renders demeclocycline useful for generating in vitro models of nephrogenic diabetes insipidus and for dissecting vasopressin receptor signaling.

Separately, as a tetracycline antibiotic, demeclocycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit and blocking aminoacyl-tRNA association with the mRNA–ribosome complex. This antimicrobial mechanism is relevant when the compound is used in studies involving bacterial systems or tetracycline-responsive gene-expression systems.

Solubility, Formulation & Handling Guidelines

Solubility: Demeclocycline hydrochloride is soluble in water and in dimethyl sulfoxide (DMSO). Solubility in ethanol is limited. For aqueous stock solutions, dissolution in sterile ultrapure water at a concentration of up to 10 mg/mL is generally achievable; however, researchers should verify solubility empirically at their intended working concentrations, as solubility can be influenced by pH and ionic strength.

Stock solution preparation: Prepare stock solutions fresh or aliquot immediately after preparation to minimize degradation. Avoid repeated freeze–thaw cycles. If preparing in DMSO, ensure that the final DMSO concentration in assay media does not exceed levels tolerated by the biological system under study (typically ≤0.1% v/v for most cell-based assays).

Stability considerations: Tetracyclines, including demeclocycline, are sensitive to light, heat, and divalent cations (Ca²⁺, Mg²⁺, Fe²⁺/³⁺). Chelation by divalent cations can significantly reduce bioavailability and activity. Avoid preparing solutions in buffers containing divalent cations (e.g., standard PBS supplemented with Ca²⁺/Mg²⁺). Store the solid compound at 2–8 °C in the dark under dry conditions.

pH sensitivity: Activity and stability are optimal near neutral to mildly acidic pH. Strongly alkaline conditions accelerate decomposition.

Research Applications

SIADH and vasopressin signaling research: Demeclocycline hydrochloride is routinely employed as a pharmacological tool to induce nephrogenic diabetes insipidus in animal models or to antagonize ADH signaling in cell-based assays. It enables researchers to study the physiological and pathological roles of AQP2 trafficking, V2 receptor signaling, and renal water homeostasis.

Oncology research: There is published interest in the potential antiproliferative and differentiation-inducing activities of tetracycline derivatives, including demeclocycline, in certain cancer cell line studies. Researchers investigating these properties should design appropriate positive and negative controls and interpret results in the context of the specific model system used.

Tetracycline-inducible gene expression systems: Although doxycycline is the most commonly used tetracycline in Tet-On/Tet-Off systems, demeclocycline may serve as a comparator or control compound in studies evaluating tetracycline-class compound cross-reactivity with tetracycline-responsive elements (TREs).

Antimicrobial tool compound: Demeclocycline can serve as a reference antibiotic in studies evaluating tetracycline resistance mechanisms, efflux pump activity, or ribosomal binding assays in relevant bacterial strains.

Quality, Purity & Regulatory Notes

Aladdin Scientific's demeclocycline hydrochloride (SKU: D113713) is supplied as a research-grade reagent intended solely for in vitro and in vivo laboratory research. It is not approved for, and must not be used in, human diagnostic, therapeutic, or food-manufacturing applications.

Researchers and procurement managers should confirm the certificate of analysis (CoA) for the specific lot received, paying attention to purity (typically assessed by HPLC), water content (Karl Fischer), and residual solvents. If a specific purity grade is required for a particular assay (e.g., ≥98% HPLC purity), this should be confirmed prior to ordering by contacting Aladdin Scientific technical support.

From a safety perspective, demeclocycline hydrochloride should be handled in accordance with the supplier's Safety Data Sheet (SDS). Standard laboratory precautions apply: avoid inhalation of dust, contact with eyes or skin, and dispose of waste in accordance with local regulations for chemical waste. Tetracyclines may cause photosensitization; minimize UV/light exposure during handling.