Liver apoptosis after dimethylnitrosamine administration in shrews

Area of Science:

• Hepatology
• Toxicology
• Cell Biology

Background:

• Dimethylnitrosamine (DMN) is a known hepatotoxin.
• Understanding the mechanisms of DMN-induced liver injury is crucial for predicting its effects and developing countermeasures.

Purpose of the Study:

• To characterize the sequential development of liver lesions induced by a single high dose of DMN in house musk shrews.
• To investigate the potential carcinogenic effect of a lower, repeated dose of DMN in the same animal model.

Main Methods:

• Female house musk shrews received a single intraperitoneal (i.p.) dose of 30 mg/kg DMN.
• Liver tissues were collected at various time points (3, 6, 16, 24, 36 hours) post-dosing for histological and ultrastructural examination.
• A separate group received two i.p. doses of 10 mg/kg DMN, and survivors were monitored for 50 weeks.

Main Results:

• A single 30 mg/kg DMN dose induced acute, fatal centrilobular liver injury characterized by apoptosis in hepatocytes and endothelial cells.
• Apoptosis was confirmed by TUNEL labeling and electron microscopy, showing characteristic nuclear condensation without mitochondrial swelling.
• A repeated lower dose (2 x 10 mg/kg DMN) did not cause acute toxicity or subsequent tumor formation over 50 weeks.

Conclusions:

• A single high dose of DMN is acutely toxic to shrew liver tissue, primarily via apoptosis.
• DMN exhibits a dose-dependent effect, with lower doses lacking carcinogenic potential in this model.