Fenvalerate-induced granulomatous changes in rats and mice
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Abstract:
Wistar rats and ddY mice were fed diet containing 10 to 3000 ppm technical fenvalerate for the major portion of their life span. Microgranulomatous changes were observed in lymph nodes, liver and spleen of both rats and mice as well as in adrenals of rats. The no-effect level for microgranulomatous changes was 30 ppm for mice and 150 ppm for rats. Transmission electron microscopy of phagocytes in the granulomatous foci revealed needle- or rod-shaped crystalline bodies within the cytoplasm. To examine reversibility of the microgranulomatous changes, ddY mice were fed the diet containing technical fenvalerate at the levels of 1000 and 3000 ppm for 6 weeks, followed by rearing on the control diet for up to 12 months. The size and number of the microgranulomatous changes were reduced with time. The microgranulomatous changes were typical of foreign body granulomas; they did not have the appearance of granulomas formed in response to immunologic stimulus.
Insights
Technical fenvalerate exposure caused microgranulomatous changes in rats and mice. These changes, identified as foreign body granulomas, showed reversibility after fenvalerate withdrawal.
Area of Science:
- Toxicology
- Pathology
Background:
- Pesticide exposure can lead to various toxicological effects.
- Understanding the long-term impact of pesticides like fenvalerate is crucial for risk assessment.
Purpose of the Study:
- To investigate the chronic effects of technical fenvalerate exposure in Wistar rats and ddY mice.
- To determine the no-effect level (NEL) for fenvalerate-induced microgranulomatous changes.
- To assess the reversibility of these observed pathological changes.
Main Methods:
- Rodents (rats and mice) were administered diets containing technical fenvalerate at doses ranging from 10 to 3000 ppm for a significant portion of their lifespan.
- Histopathological examination of various organs (lymph nodes, liver, spleen, adrenals) was performed.
- Transmission electron microscopy (TEM) was utilized to characterize cellular changes.
- Reversibility was studied by feeding high doses (1000 and 3000 ppm) for 6 weeks, followed by a control diet for up to 12 months.
Main Results:
- Microgranulomatous changes were observed in the lymph nodes, liver, and spleen of both species, and in rat adrenals.
- The no-effect levels were determined as 30 ppm for mice and 150 ppm for rats.
- TEM revealed crystalline bodies within phagocytes in granulomatous foci.
- Fenvalerate-induced microgranulomatous changes demonstrated a reduction in size and number over time following withdrawal of exposure, indicating reversibility.
Conclusions:
- Technical fenvalerate induces foreign body-type granulomas, not immunologically mediated ones.
- The observed microgranulomatous changes are reversible upon cessation of fenvalerate exposure.
- The study establishes specific no-effect levels for fenvalerate toxicity in rodents.