Low-level exposure to lead, cadmium and mercury, and histopathological findings in kidney biopsies

Abstract

Background: Lead (Pb), cadmium (Cd) and mercury (Hg) are all nephrotoxic metals, and a large part of the body burden of Cd and Hg is found in the kidneys. There are, however, few studies on associations between exposure to these toxic metals and renal biopsy findings, and none at low-level exposure.

Aim: To examine the hypothesis that low-level concentration of Pb, Cd or Hg in the kidneys is associated with histopathological changes in the kidneys.

Methods: We determined concentrations of Pb, Cd and Hg in kidney, blood and urine in 109 healthy kidney donors, aged 24-70 years. The renal biopsies were scored according to the Banff classification regarding tubular atrophy, interstitial fibrosis, glomerulosclerosis, arteriosclerosis, and arteriolohyalinosis. Kidney function was assessed based on glomerular filtration rate (GFR) as well as urinary excretion of albumin, low molecular weight proteins, kidney injury molecule 1 and N-acetylglucose aminidase. Associations between metal concentrations and histopathological changes, were assessed in models also including age, sex and smoking.

Results: The median kidney concentrations of Pb, Cd and Hg were 0.08, 13 and 0.21 μg/g, respectively. There were signs of tubular atrophy in 63%, interstitial fibrosis in 21%, glomerulosclerosis in 71%, arteriosclerosis in 47%, and arteriolohyalinosis in 36% of the donors, but, as could be expected, the histopathological findings were limited, mostly Banff grade 1. In models adjusted for age, sex and smoking, kidney Cd was positively associated with tubular atrophy (p = 0.03) and possibly with arteriolohyalinosis (p = 0.06). Kidney Hg was associated with arteriosclerosis (p = 0.004).

Discussion and conclusions: The results suggest that even low levels of Cd in the kidney can induce a mild degree of tubular atrophy. This is in line with previous findings at high-level Cd exposure. The association between kidney Hg and renal arteriosclerosis was unexpected, and may be a chance finding.

Keywords: Cadmium; Fibrosis; Kidney donor; Lead; Mercury; Tubular atrophy.