Hexavalent Chromium Induces Defense Responses,

Overview

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Key numbers

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concentrations ranging from 1.48 to 820.24 mg/kg, while Cr ranks second in water pollution
after Hg and Cd (5). Soil Cr(VI) concentrations frequently exceed 10,000 mg/kg—three
orders of magnitude above China’s screening limit of 3.0 mg/kg. Groundwater Cr(VI)
proach 10 mg/kg. Cr accumulation in soil–plant systems markedly threaten the health
of adjacent fauna and human populations (6). Xu et al. reported that 21.85% of China’s
that low-dose Cr(VI) (0.05 mg/kg and 0.25 mg/kg K2 Cr2 O7 ) disrupts hepatic mitochon-
In Japanese medaka (Oryzias latipes), Li and colleagues showed that 46% of hepatic Cr
water) and three exposure groups, each receiving 12.5 mg/L, 25 mg/L, and 50 mg/L Cr
City, which is adjacent to a ferroalloy plant, reached 28.64 mg/L (39). In addition, the
at a contaminated site in Xinxiang City, Henan Province, was as high as 10 mg/L (40).
Therefore, in our study, after final weighing and consideration, we chose to add 25 mg/L
while 12.5 mg/L and 50 mg/L were selected as the low and high doses, respectively, to
day. All animals received a commercial fattening diet formulated to contain 16% crude
protein, 2140 kcal/kg digestible energy, 22% crude fiber, 11.5% starch, 0.7% lysine, and
0.6% methionine + cysteine. The study was conducted in accordance with Chinese national
tissue blocks of 1–2 mm3 size. The tissue blocks were immediately immersed in 4% neutral
blue) and eosin (0.5% eosin alcohol solution for 2 min), followed by gradient ethanol
transferred to 1% osmium tetroxide (4 ◦ C, dark) for an additional 2 h fixation. Subsequently,
were sequentially stained with 2% aqueous uranyl acetate (dark, 30 min) and freshly
in 3% H2 O2 at room temperature in the dark for 20 min and washed three times in PBS.
carded, and the pellet was washed with 1 mL 75% ethanol, followed by centrifugation
1.48g and GraphPad Prism software. The results are expressed as the means ± standard
findings indicate that exposure to Cr(VI) at concentrations of 12.5 mg/L, 25 mg/L, and
50 mg/L exerts a discernible inhibitory effect on the blood cell indices of New Zealand
Cr level of 4.554 ± 0.66 µg/g, whereas the 50 mg/L Cr(VI) group achieved an accumulation
uniformly dark cytoplasmic staining. In the 12.5 mg/L and 25 mg/L Cr(VI) groups, inter-
staining became paler relative to controls. Administration of 50 mg/L Cr(VI) induced
with 12.5, 25, and 50 mg/L Cr(VI) results in measurable hepatic Cr accumulation in New
exhibited a modest elevation at 12.5 mg/L Cr(VI); nonetheless, this alteration was not
statistically significant (p > 0.05). Cu concentrations peaked at 25 mg/L Cr(VI), yet the
difference remained non-significant (p > 0.05), and subsequently declined at 50 mg/L, again
increase at 12.5 mg/L Cr(VI) (p > 0.05), whereas levels decreased at 25 mg/L and 50 mg/L,
with no statistical significance (p > 0.05) (Table 2). Collectively, these results demonstrate
Mn, and Se, whereas Cu levels transiently rise from 12.5 mg/L to 25 mg/L Cr(VI) before
declining from 25 mg/L to 50 mg/L Cr(VI).
profiles with intact, clearly delineated cristae. At 12.5 mg/L Cr(VI), mitochondrial mor-
cristae indistinctness. At 25 mg/L Cr(VI), mitochondrial alterations became more evident:
nucleus exhibited slight shrinkage. In the 50 mg/L Cr(VI) group, severe nuclear atrophy
were disrupted. Within apoptotic cells of the 50 mg/L Cr(VI) group, the endoplasmic retic-
yielded distinctive surface blebs. In addition, in the 50 mg/L Cr (VI) group, we found a
whereas MAP1LC3 expression increased from 0 to 25 mg/L and was marginally downregu-
lated at 50 mg/L, yet remained significantly above control levels (Figure 4C–E). Collectively,

Methods (brief)

harvested for analysis. Total Cr and essential trace elements were quantified by ICP-OES.
2.2. Sample Collection and Processing
12 h fasting period. Whole blood was collected immediately and analyzed for physiological
paper. When sampling, liver tissue samples are taken from five different liver lobules for
and snap-frozen in liquid nitrogen for gene-level analyses. Peanut-sized liver samples from
After fixation, samples were rinsed three times in 0.1 M PBS (pH 7.4), 15 min per rinse, then
ultramicrotome using a diamond knife and collected on 200-mesh copper grids. Sections
Testing Center. A minimum of three representative micrographs were captured per sample.
mRNA concentration across different samples. Reverse transcription was performed using
A microwave digestion instrument (CEM, Mars6 Xpress, Matthews, NC, USA) was
measured by inductively coupled plasma optical emission spectroscopy (ICP-OES, Analytik
in a mortar and accurately weighed 200 mg of the dry weight of the liver tissue sample.
Digestion: The tissue samples were placed in the tissue digestion tubes in order, and 6 mL
the microwave digestion instrument were as follows: 90 ◦ C for 5 min, 130 ◦ C for 5 min,
and 185 ◦ C for 25 min. Then the microwave digestion instrument was used to digest liver
tissues and release several elemental solutions to be tested. Acid rush: The digestion inner
flask and diluted to the required 15 mL. The liquid samples with a constant volume will be
After microwave digestion of liver tissue, the levels of chromium (Cr), iron (Fe),

Implications

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised