Validity of methyl mercury hair analysis: mercury monitoring in human scalp/nude mouse model.
OBJECTIVE
The grafting of human scalp hair was used as a new application of this method to explore methyl mercury incorporation into human hair and to validate this model for mercury monitoring in hair.


METHODS
Human scalp grafts were transplanted to athymic BALB/c nude mice. The animals were exposed to methyl mercury either as a single dose i.p. or continuously for 4 months, using ALZET osmotic pumps. The mercury concentration in hair was determined using x-ray fluorescence (XRF) spectrometry by segmental (2 mm) analysis of a single strand, and tissue concentrations were measured by cold vapor atomic absorption analysis.


RESULTS
Human scalp hair grown in nude mice showed long-term persistence of human features including the expression of histocompatibility antigens (KAB 3, W 6/32, SF 1-1.1.1) and normal hair morphometry. The disposition of methyl mercury in nude mice followed a one-compartment model with a whole body elimination half-life of 6.7 days (elimination constant, k = 0.1/day). Autoradiographic studies revealed that methyl mercury was rapidly incorporated into areas of the hair follicle undergoing active keratinization. Methyl mercury concentrations in human hair transplanted onto nude mice were two orders of magnitude higher than in blood and attained a mean hair: blood ratio of 217 : 1, similar to ratios reported only in human studies.


CONCLUSIONS
This study demonstrated that human hair grown on nude mice can record the level of exposure to methyl mercury and can serve as a valuable research tool to study mercury incorporation into human hair.
Zareba
Grazyna
G
Department of Environmental Medicine, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642, USA. grazyna_zareba@urmc.rochester.edu <grazyna_zareba@urmc.rochester.edu>
Cernichiari
Elsa
E
Goldsmith
Lowell A
LA
Clarkson
Thomas W
TW
D000818:Animals; D001345:Autoradiography; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D006197:Hair / Q000196:embryology / Q000254:growth & development / Q000378:metabolism* / Q000637:transplantation; D006801:Humans; D007260:Infusion Pumps; D007274:Injections, Intraperitoneal; D008767:Methylmercury Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008954:Models, Biological; D015203:Reproducibility of Results; D012535:Scalp / Q000196:embryology / Q000254:growth & development / Q000378:metabolism* / Q000637:transplantation; D013052:Spectrometry, X-Ray Emission; D013054:Spectrophotometry, Atomic
D008767:Methylmercury Compounds; C004925:methylmercuric chloride