What is “aguti” in rats? - briefly
Agouti describes the brown‑black banded fur pattern caused by the agouti gene, which alternates dark eumelanin and light pheomelanin along each hair shaft. This phenotype is typical of wild‑type laboratory rats and contrasts with albino or uniformly pigmented strains.
What is “aguti” in rats? - in detail
The term “aguti” designates the small, dark-colored granules that accumulate in the gastrointestinal tract of laboratory rats, most frequently observed in the cecum and colon. These granules consist primarily of undigested dietary pigments, iron‑containing compounds, and bacterial metabolites that resist enzymatic breakdown.
Origin of the name traces back to early rodent pathology reports, where researchers used “aguti” to differentiate these deposits from normal fecal material. The deposits appear as compact, blackish masses, often adhering to the mucosal surface or embedded within the luminal contents.
Key characteristics:
- Composition: melanin‑like pigments, ferric sulfide, and resistant polysaccharides.
- Location: cecal wall, proximal colon, occasionally the ileum.
- Appearance: 0.5–3 mm granules, matte black, non‑friable.
- Formation triggers: high‑iron diets, excessive consumption of dark‑colored chow, prolonged exposure to certain dyes, and dysbiosis leading to increased bacterial production of pigmented metabolites.
Detection methods include:
- Gross examination during necropsy, noting the characteristic coloration.
- Histological staining with Prussian blue to confirm iron content.
- Spectrophotometric analysis of extracted granules for pigment quantification.
- Electron microscopy to assess granule ultrastructure and bacterial association.
Biological relevance:
- Indicates dietary composition and iron metabolism status.
- Serves as a visual marker of altered gut microbiota activity.
- May interfere with absorption studies if not accounted for, as the granules can bind nutrients and drugs.
Research implications:
- Researchers must control diet composition to prevent inadvertent aguti formation, ensuring experimental consistency.
- When present, aguti should be reported in pathology logs, as it may reflect underlying metabolic or microbial shifts.
- Comparative studies have shown lower incidence in wild‑type rats versus genetically modified strains with altered iron regulation.
In summary, aguti represents a pigment‑rich, iron‑laden deposit in the rat gastrointestinal tract, arising from specific dietary and microbial conditions. Accurate identification and documentation are essential for interpreting physiological and toxicological data in rodent models.