Rodent hair is a Poor biomarker for internal manganese exposure

• Published in: Food and chemical toxicology 2021-11, Vol.157, p.112555, Article 112555
• Main Authors: Balachandran, Rekha C., Yanko, Frank M., Cheng, Pinjing, Prince, Lisa M., Rivers, Chloe N., Morcillo, Patricia, Akinyemi, Ayodele J., Tabbassum, Sana, Pfalzer, Anna C., Nie, Linda H., Aschner, Michael, Bowman, Aaron B.
• Format: Article
• Language: English
• Subjects: Animals; Biomarkers; Biomarkers - analysis; Female; Hair; Hair - chemistry; Injections, Subcutaneous; Male; Manganese; Manganese - administration & dosage; Manganese - adverse effects; Manganese - analysis; Manganese - pharmacokinetics; Metals; Methylmercury; Mice; Mice, Inbred C57BL; Neutron activation analysis; Rats; Rats, Sprague-Dawley; Spectrophotometry, Atomic; Tissue Distribution
• ISSN: 0278-6915; 1873-6351
• DOI: 10.1016/j.fct.2021.112555

Hair is used as a biomarker of manganese (Mn) exposure, yet there is limited evidence to support its utility to quantify internal vs external Mn exposure. C57BL/6 J mice and Sprague-Dawley rats were exposed in two blocks of 3 subcutaneous injections every 3 days starting on day 0 or 20. The control group received two blocks of saline (vehicle); Treatment A received the first block as Mn (50 mg/kg MnCl2 tetrahydrate), with the second block as either methylmercury (MeHg at 2.6 or 1.3 mg/kg) for mice or vehicle for rats; and Treatment B received Mn for both blocks. Hair was collected on days 0 and 60 from all treatment groups and Mn quantified by inductively coupled plasma-mass spectrometry (ICP-MS) and total Hg by Direct Mercury Analyzer (DMA). No correlation between internal Mn dose and hair Mn was observed, whereas hair Hg was significantly elevated in MeHg exposed vs non-exposed mice. Whole body Mn content at day 60 was quantified postmortem by neutron activation analysis, which detected significantly elevated Mn for Treatment B in mice and rats. Overall, we find no evidence to support the use of hair as a valid biomarker for internal exposure to Mn at a neurotoxic level. •Hair has potential to serve as a non-invasive biomarker for Mn exposure.•Mice and rats received sub-cutaneous Mn injections to examine accumulation in hair.•Whole body Mn was examined in mice and rats using NAA.•Sub-cutaneous MeHg exposures confirmed as a positive control.•No support for hair as a biomarker for internal Mn exposure at a neurotoxic level.