Mirex-induced adaptive liver growth: a corticosterone-mediated response

Area of Science:

• Toxicology
• Hepatology
• Endocrinology

Background:

• The liver exhibits adaptive growth in response to toxic insults.
• Hormonal regulation plays a critical role in mediating liver growth responses.
• Mirex, a persistent organochlorine pesticide, is known to affect liver function.

Purpose of the Study:

• To investigate the mechanisms of mirex-induced adaptive liver growth in rats.
• To determine the role of adrenal hormones, specifically corticosterone, in mirex-induced liver changes.
• To differentiate between hypertrophic and hyperplastic components of liver growth.

Main Methods:

• Adult male rats, both intact and adrenalectomized, were administered mirex orally.
• Relative liver weight (RLW) was measured to assess liver enlargement.
• [3H]-thymidine incorporation into hepatic DNA was used to quantify DNA synthesis and cell proliferation.

Main Results:

• Mirex administration significantly increased relative liver weight and induced DNA synthesis in intact rats.
• Adrenalectomized rats showed a blunted increase in relative liver weight but sustained DNA synthesis after mirex exposure.
• Corticosterone supplementation in adrenalectomized rats restored the relative liver weight increase but abolished the peak in DNA synthesis.

Conclusions:

• Mirex-induced adaptive liver growth comprises two distinct components: hypertrophy and hyperplasia.
• The hypertrophic component is mediated by corticosterone.
• The hyperplastic component, involving cell proliferation, is independent of corticosterone.