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Selection of a dexamethasone-resistant H-4-IIE-C3 rat hepatoma tissue-culture line
Abstract:
Exposure of H-4-IIE-C3 rat hepatoma cell cultures to the synthetic glucocorticoid, dexamethasone, results in an inhibition of cellular proliferation which is not the result of steroid-induced cytolysis. A significant decrease in both the rate of DNA synthesis and DNA content precedes a detectable effect on cell number. Continuous culture of H-IIE-C3 cells in medium containing 10(-5) M dexamethasone results in the selection of a steroid-resistant cell population that has the growth characteristics of unselected sensitive cultures and shows normal steroid induction of tryosine transaminase. Selection is a slow process requiring 24 to 36 months to obtain a phenotypically stable resistant cell line, and can be subdivided into three phases--a sensitive phase, adaptation and resistance. A comparison of the karyotypes of unselected and resistant cultures shows that the selection process enriches for a dexamethasone-resistant subpopulation.
Insights
Dexamethasone inhibits rat hepatoma cell growth without causing cell death. Long-term exposure selects for dexamethasone-resistant cells, indicating a slow adaptation process.
Area of Science:
- Cell Biology
- Pharmacology
- Biochemistry
Background:
- Glucocorticoids like dexamethasone are potent regulators of cellular processes.
- Hepatoma cell lines are valuable models for studying drug effects and resistance mechanisms.
Purpose of the Study:
- To investigate the effects of dexamethasone on H-4-IIE-C3 rat hepatoma cell proliferation.
- To characterize the selection process and properties of dexamethasone-resistant cell populations.
Main Methods:
- Exposure of H-4-IIE-C3 cells to dexamethasone (10(-5) M) in culture.
- Monitoring of DNA synthesis, DNA content, and cell number.
- Long-term culture to select for resistant cells.
- Karyotype analysis of sensitive and resistant cells.
Main Results:
- Dexamethasone inhibited cell proliferation by reducing DNA synthesis and content, not through cytolysis.
- Continuous dexamethasone exposure led to the selection of stable, steroid-resistant cells.
- Selection was a gradual process over 24-36 months, involving adaptation.
- Resistant cells retained normal growth and tyrosine transaminase induction.
Conclusions:
- Dexamethasone-induced growth inhibition in hepatoma cells is reversible and not cytotoxic.
- A subpopulation of dexamethasone-resistant cells can be selected through prolonged exposure.
- Karyotype analysis suggests enrichment of specific resistant cell variants during selection.