This short animal study gave immature female rats manganese chloride at 0, 1.0, 3.3 or 10 mg/kg body weight per day for two weeks around puberty. Ovary, uterus and oviduct weights fell at some doses, the muscle layer of the uterus changed, and serum follicle-stimulating hormone and luteinizing hormone shifted. The effects did not follow a consistent dose pattern, and puberty onset was not advanced.
Key numbers
- Ovary weight: control 22.39 ± 0.97 mg versus 19.06 ± 0.98 mg at 1 mg/kg (p < 0.05) and 17.47 ± 1.16 mg at 3.3 mg/kg (p < 0.01) (Results, pp. 296 to 297; mean ± SE, n = 8).
- Uterine weight: control 67.52 ± 5.15 mg versus 50.04 ± 2.41 mg at 3.3 mg/kg (p < 0.01); no change at 1 or 10 mg/kg (p. 297).
- Serum follicle-stimulating hormone: control 3.54 ± 0.18 ng/mL versus 3.07 ± 0.14 at 1 mg/kg (p < 0.05) and 2.75 ± 0.10 at 10 mg/kg (p < 0.01); luteinizing hormone rose from 39.85 ± 8.93 to 76.71 ± 12.36 ng/mL at 1 mg/kg (p < 0.05) (p. 297; Fig. 3, n = 6).
- Adrenal and kidney weights and body weight did not change (p. 297).
Methods (brief)
Rats received manganese chloride tetrahydrate or saline daily from postnatal day 22 to 35 and were killed on day 35. Organs were weighed, uterine sections stained with hematoxylin and eosin, and serum hormones measured by ELISA. Groups were compared with Student’s t-test.
Evidence fitness
This is an animal toxicity signal for female reproductive development during the peripubertal window. It cannot be used to derive human dose-response or dietary limits.
Limitations
Small groups, a short exposure and a non-monotonic pattern of effects. The abstract says manganese was dissolved in drinking water while the methods describe daily oral administration, and the text and abstract name different dose groups for the hormone change. Tissue manganese was not measured.
Related evidence
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