Publication: Histopathological and biochemical changes in rat thyroid following acute exposure to hexavalent chromium
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Date
2010
Authors
Mahmood, Tariq ; Zia Quresh, Irfan ; Javed Iqbal, Muhammad
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Chromium in hexavalent form is highly toxic
and a known carcinogen, although its effects on thyroid
structure and function are relatively unexplored. Workers
in an industrial environment can be, at times, exposed to
this form of chromium. The present study was, therefore,
designed using laboratory rats as a model system to
investigate the effect on thyroid structure and function
following two acute intraperitoneal doses of 30 mg/kg
b.w. potassium dichromate administered within 48
hours. The results showed that hypothalamic chromium
concentration increased (p<0.05) while thyroid
chromium concentration decreased (p<0.01).The
excretion of chromium in urine increased (p<0.05). The
treated thyroid sections revealed hyperplasia. Follicles
were disorganized, clustered and collapsed, while some
of them were fused. Interfollicular spaces widened.
Morphometrical analysis showed significantly (p<0.001)
increased number of follicles whereas the follicular size
significantly decreased (p<0.001). Nuclei were regressed
(p<0.001); nuclear shapes were irregular; round, oval
and shrunken. The membrane on the apical as well as the
basal lamina side showed disruption. Colloid retraction
within the follicles was noticeable in some sections
stained with Periodic acid Schiff (PAS). Serum free
tetra-iodothyronine (FT4) and free tri-iodothyronine
(FT3) levels decreased (p<0.01 and p<0.001,
respectively), while serum thyroid stimulating hormone
(TSH) concentration increased (p<0.01). Ultrastructural
analysis showed disrupted basal laminae of the follicles,
regressed nuclei and disrupted cell organelles. Acridine
orange stained thyroid cells demonstrated excessive dead
cells, whereas DNA fragmentation assay demonstrated
percent decrease of hypothalamic, pituitary and thyroidal
total DNA.
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