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    • Parathyroid hormone (1-34) (human): Mechanistic Precision...

    2026-03-17

    Parathyroid hormone (1-34) (human): Mechanistic Precision in Calcium Homeostasis and Bone Research

    Executive Summary: Parathyroid hormone (1-34) (human) is a rigorously characterized peptide fragment of the human parathyroid hormone, comprising the first 34 amino acids and exhibiting a molecular weight of 4117.72 Da (APExBIO). Its primary mechanism is activation of parathyroid hormone 1 and 2 receptors (PTH1R/PTH2R), leading to robust cAMP and inositol phosphate signaling cascades in target cells (Huang et al., 2025). In vitro, the peptide demonstrates an IC50 of 0.22 nM for cAMP stimulation in human kidney 293 cells. In vivo studies confirm dose- and time-dependent increases in trabecular and cortical bone mass in rat models. High solubility in water (≥19.88 mg/mL) and DMSO (≥399.3 mg/mL), combined with >97.8% purity, make it a gold standard reagent in bone metabolism and kidney disease modeling (APExBIO).

    Biological Rationale

    Parathyroid hormone (1-34) (human), also known as PTH (1-34), is a bioactive peptide fragment derived from the N-terminus of the full-length human parathyroid hormone. It is secreted by chief cells of the parathyroid glands and plays a central role in the regulation of serum calcium and phosphate homeostasis. The peptide exerts its biological activities by interacting with specific G protein-coupled receptors (GPCRs), namely PTH1R and PTH2R, located on bone, kidney, and other target tissues (Huang et al., 2025). The regulatory effects of PTH (1-34) on bone remodeling and renal calcium handling make it a critical tool for elucidating mechanisms underlying osteoporosis, chronic kidney disease, and calcium metabolism disorders.

    Mechanism of Action of Parathyroid hormone (1-34) (human)

    PTH (1-34) binds with high affinity to the parathyroid hormone 1 receptor (PTH1R) and, to a lesser extent, PTH2R, both of which are members of the class B GPCR family (Huang et al., 2025). Upon receptor engagement, PTH (1-34) initiates a signaling cascade that involves Gs protein activation, leading to increased intracellular cyclic AMP (cAMP) and subsequent activation of protein kinase A (PKA). This pathway regulates the expression of genes involved in calcium and phosphate transport, bone resorption, and mineralization. In addition to cAMP, PTH (1-34) can stimulate inositol phosphate (IP3) production through Gq protein coupling, further diversifying its downstream effects. In human kidney 293 cells transfected with PTH1R, PTH (1-34) induces cAMP accumulation with an IC50 of approximately 0.22 nM, establishing its potency as a receptor agonist (APExBIO).

    Mechanistically, PTH (1-34) increases calcium efflux from bone by promoting osteoclast-mediated bone resorption. It enhances renal tubular reabsorption of calcium and magnesium, particularly in the distal convoluted tubule and thick ascending limb of Henle. Furthermore, PTH (1-34) stimulates the synthesis of 1,25-dihydroxyvitamin D (calcitriol) in the kidney, boosting intestinal calcium absorption (Huang et al., 2025).

    Evidence & Benchmarks

    • PTH (1-34) (human) binds PTH1R and stimulates cAMP production in HEK293 cells with an IC50 of 0.22 nM (APExBIO).
    • In vivo, subcutaneous dosing (10 or 40 μg/kg/day) in male Fisher 344 rats results in dose- and time-dependent increases in trabecular and cortical bone mass (APExBIO).
    • PTH (1-34) upregulates renal 1α-hydroxylase, increasing serum 1,25-dihydroxyvitamin D and enhancing intestinal calcium absorption (Huang et al., 2025).
    • Solubility profile: ≥399.3 mg/mL in DMSO, ≥19.88 mg/mL in water, insoluble in ethanol (APExBIO).
    • PTH (1-34) is validated for use in advanced spatially patterned kidney assembloid models, recapitulating kidney progenitor self-assembly and signaling fidelity (Huang et al., 2025).

    This article extends recent work on mechanistic workflows by providing updated quantitative benchmarks for cAMP signaling and solubility, clarifying integration with advanced assembloid models. It also augments the translational paradigm by detailing precise handling and solubility advice, and updates the cell assay optimization article with validated experimental parameters.

    Applications, Limits & Misconceptions

    PTH (1-34) is widely used in bone metabolism research, osteoporosis modeling, and advanced kidney disease platforms, including spatially patterned human kidney assembloids. Its capacity to precisely modulate PTH/PTHrP receptor signaling makes it an indispensable reagent for dissecting complex endocrine and paracrine signaling in vitro and in vivo (Huang et al., 2025).

    Common Pitfalls or Misconceptions

    • Diagnostic/Medical Use: PTH (1-34) (human) from APExBIO is strictly for research use; it is not validated for diagnostic or therapeutic applications (APExBIO).
    • Solubility Constraints: The peptide is insoluble in ethanol; attempting dilution in this solvent results in precipitation and loss of activity.
    • Storage Protocol: Long-term storage of diluted solutions is discouraged; freshly prepared aliquots are required to maintain bioactivity.
    • Species-Specific Activity: While PTH (1-34) is highly active in rodent and human models, functional equivalence in other species should be empirically validated.
    • Overreliance on cAMP Readout: Not all biological effects are mediated via cAMP; parallel monitoring of inositol phosphate and downstream gene targets may be necessary for full mechanistic insight.

    Workflow Integration & Parameters

    For experimental use, PTH (1-34) (human) is supplied as a solid and should be stored desiccated at -20°C. Prior to use, dissolve in DMSO (≥399.3 mg/mL) or water (≥19.88 mg/mL); avoid ethanol. Prepare fresh aliquots for each experiment to ensure maximal activity. In cell-based assays, recommended working concentrations range from 0.1 to 100 nM, with validation of cAMP or inositol phosphate signaling as readouts. In animal models, subcutaneous dosing protocols typically use 10–40 μg/kg/day for 2–4 weeks to assess bone or kidney endpoints (APExBIO).

    Recent advances in kidney assembloid technology, such as those described by Huang et al., enable high-fidelity disease modeling platforms that accurately recapitulate in vivo progenitor self-assembly and organ-specific signaling (Huang et al., 2025). The integration of rigorously characterized peptides like PTH (1-34) facilitates reproducible and physiologically relevant data, supporting translational research in bone and kidney disorders. For a detailed contrast with prior cell assay optimization protocols, see this guide.

    Conclusion & Outlook

    Parathyroid hormone (1-34) (human) from APExBIO remains a foundational reagent for bone metabolism and kidney research. Its validated activity, high purity, and well-defined mechanism of action make it a preferred tool in both classical and next-generation experimental systems. As advanced assembloid and organoid models mature, precise control of PTH/PTHrP receptor signaling using PTH (1-34) will underpin further breakthroughs in disease modeling and regenerative medicine. For product details and ordering, refer to the official APExBIO product page (SKU A1129).