Changes in the activities of protein kinases A,C, and M in dog heart and liver following endotoxin administration

Abstract

Changes in the activities of protein kinase A (cAMP-dependent), protein kinase C (Ca 2+/phospholipid-dependent), and protein kinase M (Ca 2+/calmodulin-dependent) in dog heart and liver were studied 4 hr following endotoxin injection. Protein kinases A and C were extracted and partially purified by DEAE-cellulose chromatography. Protein kinase M was extracted and partially purified by DEAE-cellulose, DEAE-Sephacel, and calmodulin-Sepharose chromatography. The results indicate that in the heart, both type I (eluted at low ionic strength) and type II (eluted at high ionic strength) protein kinase A activities were unchanged after endotoxin administration. Cardiac cytosolic protein kinase C activity was increased by 50% (p<0.05) while the membrane-associated protein kinase C activity remained unaltered following endotoxin injection. Cardiac protein kinase M activity was decreased by 38.5% (p<0.01) post endotoxin. In the liver, type I protein kinase A activity was unaffected while type II protein kinase A activity was decreased by 34% (p<0.01) following endotoxin injection. Hepatic cytosolic and membrane-associated protein kinase C activities were inhibited by 37% (p<0.01) and 53% (p<0.01), respectively, 4 hr postendotoxin. Hepatic protein kinase M activity was decreased by 61% (p<0.01) after endotoxin administration. These data indicate that the activities of various protein kinases in the heart and liver were modified by endotoxin administration. Since protein kinases regulate cell function through phosphorylation of various substrate proteins, a modification on protein kinase activities may contribute to the development of organ dysfunction in endotoxin shock.