Dexamethasone induction of an inhibitor of plasminogen activator in HTC hepatoma cells

Incubation of HTC rat hepatoma cells with dexamethasone causes a rapid decrease in cellular plasminogen activator (PA) activity. Mixing experiments show the presence of an inhibitor of PA in dexamethasone-treated cells. This study investigates whether the decrease in PA activity is secondary to the...

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Bibliographic Details
Published in:The Journal of biological chemistry 1984-06, Vol.259 (11), p.6847-6851
Main Authors: Cwikel, B J, Barouski-Miller, P A, Coleman, P L, Gelehrter, T D
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Blood coagulation. Blood cells
Cycloheximide - pharmacology
Dactinomycin - pharmacology
Dexamethasone - pharmacology
Drug Resistance
Electrophoresis, Polyacrylamide Gel
Fundamental and applied biological sciences. Psychology
General aspects, investigation methods, hemostasis, fibrinolysis
Liver Neoplasms, Experimental - metabolism
Macromolecular Substances
Molecular and cellular biology
Molecular Weight
Plasminogen Activators - antagonists & inhibitors
Plasminogen Inactivators
Rats
Time Factors
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Summary:Incubation of HTC rat hepatoma cells with dexamethasone causes a rapid decrease in cellular plasminogen activator (PA) activity. Mixing experiments show the presence of an inhibitor of PA in dexamethasone-treated cells. This study investigates whether the decrease in PA activity is secondary to the induction of an inhibitor by glucocorticoids, to a decrease in the amount of PA, or to a combination of both mechanisms. PA and its inhibitor are dissociated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under non-reducing conditions, and both activities are then recovered and quantitated. HTC cells have two major forms of PA with Mr values of 110,000 and 64,000. Although PA activity in the unfractionated extracts from dexamethasone-treated cells is inhibited by 90% relative to control, there is no decrease in the total activity of sodium dodecyl sulfate-dissociated PA activity, suggesting that dexamethasone causes no decrease in the amount of the enzyme. PA inhibitor activity migrates as a single band of Mr = 50,000. The total activity of inhibitor increases in a time-dependent fashion, reaching a maximum of greater than 10 times control after a 4-6-h incubation with 0.1 microM dexamethasone. The induction of inhibitor requires both RNA and protein synthesis and shows a dependence on dexamethasone concentration identical to that for responses known to be mediated by glucocorticoid receptors. We conclude that dexamethasone inhibits PA activity by inducing the synthesis of an inhibitor rather than by decreasing the amount of PA.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(17)39805-8