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Relationship between nucleolar microspherule formation by urethan and inhibition of RNA and protein synthesis
Abstract:
Liver tissues of suckling C3Hf mice treated with urethan, a carcinogen and inhibitor of RNA synthesis, and with cycloheximide, an inhibitor of protein synthesis, were studied by electron microscopy and by light microscope radioautography. At 4 and 12 hr after treatment with a single dose of urethan (1 mg/g body weight). [3H]uridine incorporation in hepatocyte nuclei was 38 and 9% lower than in controls and became 32% higher at 24 hr. Nucleolar microspherules were found 1.5 and 4 hr after the treatment, increased considerably in number at 10 and 12 hr, and decreased at 24 hr. These results suggest an inverse relationship between RNA synthesis and formation of microspherules. Cycloheximide alone (3 mg/kg body weight) produced microspherules, whereas in combination with a dose of 1 or 2 mg of urethan per g body weight it partially prevented or potentiated, respectively, the microspherule production.
Insights
Urethane, a carcinogen, inhibits RNA synthesis and affects liver cell microspherules. Cycloheximide, a protein synthesis inhibitor, also impacts microspherule formation, suggesting an inverse relationship with RNA synthesis.
Area of Science:
- Hepatology
- Molecular Biology
- Carcinogenesis
Background:
- Urethane is a known carcinogen that inhibits RNA synthesis.
- Cycloheximide is an inhibitor of protein synthesis.
- Investigating the effects of these agents on liver tissue is crucial for understanding cellular responses to chemical insults.
Purpose of the Study:
- To investigate the impact of urethane and cycloheximide on liver tissue at the cellular level.
- To examine the relationship between RNA synthesis inhibition and the formation of nucleolar microspherules.
- To determine the combined effects of urethane and cycloheximide on microspherule production.
Main Methods:
- Electron microscopy was used to examine liver tissue ultrastructure.
- Light microscope radioautography with [3H]uridine was employed to quantify RNA synthesis.
- Mice were treated with urethane and/or cycloheximide at specific dosages and time points.
Main Results:
- Urethane treatment led to decreased [3H]uridine incorporation in hepatocyte nuclei at early time points, with a subsequent increase.
- Nucleolar microspherules appeared after urethane treatment, increased in number, and then decreased.
- Cycloheximide alone induced microspherules, while its combination with urethane showed varied effects on microspherule production.
Conclusions:
- There appears to be an inverse relationship between hepatic RNA synthesis and the formation of nucleolar microspherules.
- Both urethane and cycloheximide influence microspherule formation in liver cells.
- The interplay between protein and RNA synthesis inhibition affects microspherule production in a dose-dependent manner.
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