Norepinephrine-Sensitive Properties of C-6 Astrocytoma Cells
C-6 astrocytoma cells respond to 0.1 mM norepinephrine by a greater than 200-fold elevation of adenosine cyclic 3', 5'-monophosphate (cAMP) and an 80% degradation of glycogen during 20 min of incubation in Hamâs F-10 medium. Evaluation of the time course of these effects indicated that g...
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Veröffentlicht in: | Molecular pharmacology 1974-01, Vol.10 (1), p.162-174 |
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Zusammenfassung: | C-6 astrocytoma cells respond to 0.1 mM norepinephrine by a greater than 200-fold elevation
of adenosine cyclic 3', 5'-monophosphate (cAMP) and an 80% degradation of glycogen
during 20 min of incubation in Hamâs F-10 medium. Evaluation of the time course of these
effects indicated that glycogenolysis occurred nonlinearly at a rate of 1-2 nmoles/min/mg
of protein; cAMP was maximally elevated after 5 min of incubation and remained so for the
30-min experiment. Norepinephrine induced transformation of glycogen phosphorylase to
the 3'-AMP-independent or a form during the first 30 sec of incubation. At the time when
phosphorylase a formation had begun, 5 sec after norepinephrine addition, cAMP was elevated only 10-fold. During a 3-hr treatment of cells
with norepinephrine, cAMP and glycogen
concentrations returned to nearly control concentrations; yet incubation fluid retained
sufficient norepinephrine to elevate cAMP as before in fresh samples of cells. Treatment of
C-6 cells with norepinephrine for 3 hr followed by 1 hr of incubation without hormone
largely suppressed the effect of a second norepinephrine treatment on cAMP concentration,
but glycogenolysis occurred as before. 1-Methyl-3-isobutylxanthine, an inhibitor of cAMP
phosphodiesterase, partially overcame the suppression of the norepinephrine effects when
added with norepinephrine. It is concluded that C-6 astrocytoma cells contain a norepinephrine-activated system of enzymes
for degrading glycogen and that norepinephrine
treatment modifies the response of the cells to subsequent exposure to this neurohormone. |
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ISSN: | 0026-895X 1521-0111 |