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A Quantitative Morphometric Analysis of the Effects of Sub‐Chronic Cadmium Exposure on the Proximal Tubule of the Rat
Author(s) -
Hublikar Ishaan,
Edwards Joshua R,
Lamar Peter C,
Gasiorowski Joshua Z,
Prozialeck Walter C
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.819.4
Subject(s) - proximal tubule , saline , renal injury , cadmium , pathology , kidney , medicine , nephrotoxicity , chemistry , tubule , renal cortex , beagle , organic chemistry
Cadmium (Cd) is a nephrotoxic environmental pollutant that causes insidious injury to the proximal tubule that results in polyuria and proteinuria. Previous studies from our laboratory have shown that the early stages of Cd‐induced kidney injury may involve disruption of the adhering junctions between epithelial cells of the proximal tubule. In the present study, we utilized the Image J computer program to quantify the effects of sub‐chronic Cd exposure on the morphology of the rat proximal tubule. Adult male Sprague‐Dawley rats (n=6) were treated with CdCl 2 (0.6 mg/kg, in saline vehicle) by subcutaneous injection, 5 days per week for 12 weeks, while control animals (n=6) received saline vehicle alone. At the end of the treatment period, 24 hour urine samples were collected and assayed for levels of protein, cystatin C, beta‐2 microglobulin and kidney injury molecule 1 (Kim 1). In addition, the animals were euthanized and the kidneys were removed, fixed in formalin and processed for histopathologic analysis. Hematoxylin/eosin‐stained sections (4 microns thick) were viewed using a 40× objective lens, and digital images (n=15 control and 15 Cd‐treated) of the renal cortex were captured. The Image J computer program was used to identify, by hand drawing, cross‐sections of proximal tubules (n=5–8 per image). In addition, Image J was used to define individual components of the cross‐sectional images of proximal tubules. Specific components that were defined included: total cross sectional area, luminal cross sectional area, area of gaps between cells and total cellular area. The results showed that Cd caused an increase in urine volume and urinary levels of protein, Kim 1, beta‐2 microglobulin and cystatin C, with no change in creatinine excretion. The morphometric analyses showed that Cd had no significant effect on total cross sectional tubular area or cellular area. However, it caused a slight decrease (36%, p<0.01) in luminal cross sectional area and a marked increase (300%, p<0.001) in gap areas between cells. Additional studies indicated that at the time these changes were occurring, there was no evidence of necrosis and only a slight increase in the number of apoptotic cells in the proximal tubule. These results are consistent with previous findings suggesting that the early stages of Cd‐nephrotoxicity involve the disruption of epithelial cell‐cell junctions in the proximal tubule. Support or Funding Information Supported by restricted funds from the Department of Pharmacology, Midwestern University.