ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
S49.1 Lymphoma cells were arrested in G1 phase of the cell cycle when treated with either 1 μM dexamethasone (Dex) or 0.5 mM N6, O2-dibutyryl cyclic adenosine 3′ :5′ -monophosphate (Bt2cAMP) plus 0.2 mM theophylline. However, the two agents had markedly different effects on aspects of polyamine and cyclic nucleotide metabolism within the arrested cells. Bt2cAMP had an early and pronounced inhibitory effect on ornithine decarboxylase (ODC) activity causing a decrease to 40% of control within 1 h. However, there was no significant inhibition of ODC activity in the Dex-treated cells until 4 h of exposure, at which time ODC activity was reduced to approximately 60% of the control value. Sadenosyl-L-methionine decarboxylase (SAMD) activity was reduced by both agents, Bt2cAMP having the more pronounced inhibitory effect. The activity of SAMD was reduced to 40% of control after 10 h of Dex, whereas Bt2cAMP reduced the activity to approximately 25% of control within 4 h. Intracellular polyamine pools were decreased rapidly in Dex-treated cells but not in those exposed to Bt2cAMP. Bt2cAMP decreased the amount of type I (PKI) and type II (PKII) cyclic AMP-dependent protein kinase (cAMP-PK) activity to 30% of control or less within 2 h. In contrast, Dex had very little effect on either PKI or PKII until 24 h, when cell viability was affected. The specific activity of both PKI and PKII remained significantly decreased in cells exposed to Bt2cAMP for 6 h and then resuspended in fresh medium. The rapid decrease in ODC activity in response to Bt2cAMP and the slow recovery after washout may be due to the marked decreases in total PKI and PKII activities. Dex, which had no effect on PKI and PKII specific activities, only slowly inhibited ODC activity and recovery of enzyme activity was rapid upon resuspension in fresh medium. These data further stress the importance of the maintenance of the cellular protein kinase pools in the regulation of the recovery time to growth inhibition in response to naturally occurring steroids and second messengers.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041060307
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