How does ammonia affect mice? - briefly
Inhaled ammonia irritates the respiratory tract of rodents, causing airway inflammation, impaired gas exchange, and reduced oxygen saturation. At elevated levels it leads to weight loss, altered locomotor behavior, and increased mortality.
How does ammonia affect mice? - in detail
Ammonia exposure in laboratory rodents produces dose‑dependent respiratory, neurological, and systemic alterations. Inhalation of concentrations above 25 ppm causes irritation of the nasal epithelium, leading to increased mucus secretion, ciliary dysfunction, and epithelial hyperplasia. Chronic exposure at 10–20 ppm results in persistent inflammation, thickened airway walls, and reduced lung compliance, measurable by decreased tidal volume and increased respiratory resistance.
Neurological effects appear at both acute and prolonged exposure. Short‑term bursts of 100 ppm for minutes elevate blood ammonia levels, crossing the blood‑brain barrier and impairing astrocyte function. Observable outcomes include reduced locomotor activity, impaired coordination on rotarod tests, and delayed reflexes. Chronic exposure (≤10 ppm for weeks) is associated with altered neurotransmitter ratios, particularly decreased glutamate clearance, contributing to anxiety‑like behavior and impaired learning in maze tasks.
Growth and reproductive parameters are sensitive to sub‑lethal concentrations. Studies report a 5–10 % reduction in body weight gain in weanlings exposed to 15 ppm for 6 h day⁻¹, accompanied by decreased feed efficiency. Female fertility declines when dams experience continuous 5–10 ppm exposure during gestation: litter size drops by 15 %, and neonatal mortality rises due to compromised placental vascularization.
Immune function deteriorates under sustained ammonia presence. Elevated serum cortisol and reduced lymphocyte proliferation have been documented after 4 weeks of 12 ppm exposure. Pulmonary macrophage activity diminishes, increasing susceptibility to bacterial pneumonia in challenge models.
Metabolic disturbances include altered kidney function, reflected by increased blood urea nitrogen and reduced creatinine clearance at 20 ppm exposure. Hepatic enzyme activity (ALT, AST) rises modestly, indicating mild hepatocellular stress.
Typical experimental design employs whole‑body exposure chambers with controlled humidity and temperature. Monitoring includes:
- Airborne ammonia concentration (ppm) measured by photoacoustic spectroscopy.
- Respiratory parameters via plethysmography.
- Blood ammonia, cortisol, and cytokine panels.
- Histopathology of nasal, lung, brain, and liver tissues.
- Behavioral assays: open‑field, elevated plus‑maze, rotarod.
Threshold values derived from multiple studies suggest:
- ≤5 ppm: negligible acute effects, minor chronic changes after >8 weeks.
- 5–15 ppm: measurable respiratory irritation, modest weight impact, subtle behavioral shifts.
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15 ppm: pronounced inflammation, significant neurobehavioral deficits, reproductive impairment.
Mitigation strategies focus on ventilation upgrades, ammonia scrubbers, and regular air‑quality assessments to maintain concentrations below the 5 ppm threshold, thereby preserving animal welfare and experimental integrity.