Liver and renal lesions in mercury-contaminated narwhals (Monodon monoceros) from North West Greenland

Abstract

Narwhals (Monodon monoceros) from North West Greenland are known to bioaccumulate mercury (Hg) in tissues and internal organs. This is postulated to be a health concern and therefore studies were undertaken to conduct a screening study of Hg concentrations and histopathology of liver and renal tissues in a total of 12 specimens. The sample consisted of two sub-adults (one male, one female) and 10 adult (six males, four females) collected in Qaanaaq (Thule) 2010. In liver, Hg mean ± SD was 11.88 ± 10.47 μg/g ww (range: 0.39−31.8 μg/g ww) while the concentrations in kidneys were 1.85 ± 1.20 μg/g ww (range: 0.41−4.03 μg/g ww). There was no marked difference in Hg concentrations between males and females while sub-adults had significantly lower concentrations. The histological examinations of renal tissue showed glomerular capillary dilatation and basement membrane thickening, dilatation, and hyalinization of Bowman's space/capsule and tubular lesions with hyaline casts accompanied by interstitial fibrosis in the kidneys. In liver tissue, portal cell infiltrates and fibrosis, bile duct proliferation, lipid-filled Ito cells, and steatosis were found. There was no marked difference in histological prevalence between males and females and in Hg concentrations in individuals with or without lesions. Four of seven renal lesions and one liver lesion were found in the two sub-adult whales. Based upon these findings, as well as the nature of the lesions, evidence suggests that histopathological alterations were a result of age but that Hg might be an aggravating co-factor in development of renal lesions in particular.