Reversal of catecholamine refractoriness by inhibitors of RNA and protein synthesis
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Abstract:
The generation of adenosine 3',5'-monophosphate (cyclic AMP) in response to catecholamines in the 2B subclone of RGC6 rat glioma cells previously exposed to norepinephrine and refractory to further norepinephrine addition is substantially increased by addition of inhibitors of RNA and protein synthesis. The time course of the effect of these inhibitors on cyclic AMP concentration suggests that rapid protein synthesis and turnover are involved in catecholamine refractoriness. Norepinephrine induction of cyclic nucleotide phosphodiesterase is demonstrable in RGC6 cells but not in the 2B subclone. Thus, catecholamine refractoriness cannot be attributed to induction of phosphodiesterase. This implies that induction of a protein or proteins, important in catecholamine refractoriness, affects the synthesis rather than the degradation of cyclic AMP.
Insights
Inhibitors of RNA and protein synthesis increase cyclic AMP in refractory cells, suggesting rapid protein turnover is key to catecholamine refractoriness. This refractoriness is not due to phosphodiesterase induction.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- RGC6 rat glioma cells exhibit refractoriness to catecholamine stimulation after prior exposure.
- Understanding the mechanisms of this refractoriness is crucial for cellular signaling research.
Purpose of the Study:
- To investigate the mechanisms underlying catecholamine refractoriness in the 2B subclone of RGC6 cells.
- To determine if phosphodiesterase induction contributes to this phenomenon.
Main Methods:
- Treatment of 2B RGC6 cells with norepinephrine to induce refractoriness.
- Addition of RNA and protein synthesis inhibitors to refractory cells.
- Measurement of cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels.
- Assessment of norepinephrine-induced cyclic nucleotide phosphodiesterase activity.
Main Results:
- Inhibitors of RNA and protein synthesis significantly increased cyclic AMP generation in refractory cells.
- The time course indicated rapid protein synthesis and turnover are involved in refractoriness.
- Norepinephrine did not induce cyclic nucleotide phosphodiesterase in the 2B subclone, unlike parent RGC6 cells.
Conclusions:
- Catecholamine refractoriness in 2B RGC6 cells is not mediated by phosphodiesterase induction.
- The findings imply that induced proteins affecting cyclic AMP synthesis, not degradation, are critical for catecholamine refractoriness.