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Urinary protein excretion of semidomesticated mink in a chronic methylmercury study
G Chamberland1, D Bélanger, A Dallaire
1Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada.
Abstract:
A model using semidomesticated mink was set up to study the effects of chronic oral methylmercury exposure in piscivorous mammals. Three groups of mink were fed daily with diets containing approximately 0.1, 0.5, and 0.9 micrograms/g of total mercury. Piscivorous and non-piscivorous fish, naturally contaminated with methylmercury, were used to prepare diets. Renal injury was evaluated using total urine protein/creatinine ratio and differentiation of urinary low-molecular-weight and high-molecular-weight proteins on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The significance of the total urine protein/creatinine ratio data was assessed by comparing the results to a 95% group-based reference interval. The values for total urine protein/creatinine ratio did not reveal any significant increased excretion, and no dose-related trends were observed within the reference interval. Overall the total urine protein data did not suggest renal damage. Analysis of the SDS-PAGE electrophoretograms did not suggest the presence of any persistent glomerular damage in any group. High-molecular-weight proteins were not detected more frequently for any of the dose groups. During the adaptation phase, the B2M-like protein band was not remarked during the visual analysis of the gels. The B2M-like protein band was remarked during the gel analysis only several weeks into the exposure phase. This B2M-like protein band was more prevalent in urine samples taken from minks in the 0.5 and 0.9 micrograms/g groups than in the 0.1 microgram/group. These latter data, however, did not allow an evaluation of a quantitative dose-response excretion with time. The B2M-like data are suggestive of very minor renal injury.
Insights
Chronic methylmercury exposure in mink did not cause significant renal damage, though a specific protein band suggested minor kidney injury at higher doses. This study informs on mercury toxicity in fish-eating mammals.
Area of Science:
- Environmental toxicology
- Mammalian physiology
- Biomarker discovery
Background:
- Methylmercury is a neurotoxin biomagnifying in aquatic food webs.
- Piscivorous mammals are at risk of methylmercury accumulation.
- Assessing renal effects of chronic mercury exposure is crucial for wildlife health.
Purpose of the Study:
- To investigate the effects of chronic oral methylmercury exposure on mink kidneys.
- To evaluate renal injury using urine protein analysis and SDS-PAGE.
- To establish dose-response relationships for mercury-induced renal toxicity.
Main Methods:
- A controlled study using semidomesticated mink exposed to methylmercury via contaminated fish diets.
- Quantification of total urine protein/creatinine ratio.
- Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) for urinary protein differentiation.
Main Results:
- Total urine protein/creatinine ratios showed no significant increase or dose-related trends, indicating no substantial renal damage.
- SDS-PAGE analysis did not reveal persistent glomerular damage.
- A B2M-like protein band appeared in higher-dose groups (0.5 and 0.9 µg/g), suggesting very minor renal injury.
Conclusions:
- Chronic methylmercury exposure at the tested levels did not induce significant renal damage in mink.
- The B2M-like protein band may serve as a sensitive indicator of minimal renal injury.
- Further research is needed to quantify the dose-response of this biomarker over time.
