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Distribution of the liver carcinogen methapyrilene in Fischer rats and its interaction with macromolecules
Abstract:
The anti-histaminic drug methapyrilene hydrochloride, which induces liver tumors in ras, was labeled with tritium by exchange and administered at a does of 21 mg containing 700 microCi to each of 15 male Fischer rats. At 1 h, 6 h, 14 h, 24 h, and 44 h after treatment three rats were killed and their livers, pancreas, kidneys, and lungs were removed. The pooled organs were homogenized and DNA, RNA, and soluble protein were isolated from each. The extent of interaction of radioactive methapyrilene with liver nucleic acids was exceedingly small and did not differ significantly from the binding to nucleic acids in kidney, lung, or pancreas, which are not target organs of this carcinogen in rats. Binding of radioactivity to soluble proteins of the liver was considerable and substantially greater than in the other organs. If the mechanism of carcinogenic action of methapyrilene involves covalent interaction with DNA this must be at a very low and highly specific level.
Insights
The carcinogen methapyrilene hydrochloride showed minimal interaction with liver nucleic acids in rats. Binding to liver soluble proteins was significant, suggesting a potential mechanism for its liver tumor-inducing effects.
Area of Science:
- Toxicology
- Carcinogenesis
- Biochemistry
Background:
- Methapyrilene hydrochloride is an antihistaminic drug known to induce liver tumors in rats.
- Understanding the molecular mechanisms of drug-induced carcinogenesis is crucial for public health.
Purpose of the Study:
- To investigate the interaction of radiolabeled methapyrilene hydrochloride with nucleic acids and proteins in rat organs.
- To explore the potential role of DNA interaction in methapyrilene-induced liver tumorigenesis.
Main Methods:
- Tritium-labeled methapyrilene hydrochloride was administered to male Fischer rats.
- Organs (liver, pancreas, kidneys, lungs) were collected at various time points post-administration.
- DNA, RNA, and soluble proteins were isolated and analyzed for radioactivity.
Main Results:
- Interaction of methapyrilene with liver nucleic acids (DNA, RNA) was minimal and not significantly different from non-target organs.
- Substantial binding of radioactivity was observed with soluble liver proteins.
- The extent of DNA interaction was exceedingly small, even in the target organ.
Conclusions:
- The carcinogenic mechanism of methapyrilene hydrochloride may not primarily involve extensive covalent interaction with liver DNA.
- Significant binding to soluble liver proteins warrants further investigation regarding its role in carcinogenesis.
- If DNA interaction is involved, it must be at a very low and highly specific level.