Liver protein kinases in shock: I. Endotoxin administration inactivates protein kinase a in dog liver

Effects of endotoxin administration on protein kinase A (cAMP-dependent protein kinase) activity in dog liver were investigated. Hepatic protein kinase A was extracted and partially purified by acid precipitation, ammonium sulfate fraction, and DEAE-cellulose chromatography. Protein kinase A was elu...

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Bibliographic Details
Published inShock (Augusta, Ga.) Vol. 3; no. 6; p. 411
Main Authors Hsu, H K, Yang, S L, Tao, Y P, Liu, M S
Format Journal Article
LanguageEnglish
Published United States 01.06.1995
Subjects
Animals
Cyclic AMP - metabolism
Cyclic AMP-Dependent Protein Kinase Type II
Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors
Dogs
Endotoxins - administration & dosage
Endotoxins - pharmacology
Injections, Intravenous
Liver - enzymology
Magnesium - pharmacology
Male
Shock - enzymology
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Summary:Effects of endotoxin administration on protein kinase A (cAMP-dependent protein kinase) activity in dog liver were investigated. Hepatic protein kinase A was extracted and partially purified by acid precipitation, ammonium sulfate fraction, and DEAE-cellulose chromatography. Protein kinase A was eluted from DEAE-cellulose column with a linear NaCl gradient. Two peaks of protein kinase A, type I (eluted at low ionic strength) and type II (eluted at high ionic strength), were collected, and their activities were determined based on the rate of incorporation of [gamma-32P]ATP into histone. The results obtained 4 h after endotoxin administration (.5 mg/kg, intravenously) show that type I protein kinase A activity was unaffected, while type II protein kinase A activity was inhibited by 26-57%. Kinetic analysis of the data on type II protein kinase A reveals that the Vmax values for ATP, cAMP, and histone were decreased by 31, 39, and 36%, respectively; while the S.5 (substrate concentration required for half-maximal enzyme activity) values for ATP, cAMP, and histone were unaffected following endotoxin administration. These data indicate that endotoxin administration inhibits hepatic type II protein kinase A activity and the nature of inhibition is by a mechanism not competing with ATP, cAMP, and histone reactive sites. Since protein phosphorylation plays an important role in the regulation of cell metabolism and function, our finding may contribute to the understanding of hepatocellular dysfunction during endotoxin shock.
ISSN:1073-2322