INACTIVATION OF PROTEIN-KINASE-C IN RAT-LIVER DURING LATE HYPOGLYCEMIC PHASE OF SEPSIS

Changes in protein kinase C (PKC) (calcium-and phospholipid-dependent protein kinase) activity in rat liver during different metabolic phase s of sepsis were studied. Sepsis was induced by cecal ligation and pun cture (CLP). Experiments were divided into three groups: control, earl y sepsis, and late sepsis. Early and late sepsis refers to those anima ls sacrificed at 9 and 18 h, respectively, after CLP. Hepatic PKC was extracted and partially purified by ammonium sulfate fractionation and DEAE-cellulose chromatography. PKC activity was assayed based on the rate of incorporation of (32)p from [gamma-P-32]ATP into histone. The results show that during early sepsis, both membrane-associated and cy tosolic PKC activities remained relatively unaltered. During late seps is, membrane-associated PKC was unaffected while cytosolic PKC activit y was decreased by 19.5-34.4%. Kinetic analysis of the data on cytosol ic PKC during late phase of sepsis reveals that the V-max values for A TP, histone, Ca2+, phosphatidylserine, and diacylglycerol were decreas ed by 23.4, 22.1, 19.5, 25, and 34.4%, respectively, with no changes i n their Km values. These data indicate that cytosolic PKC activity was inactivated in rat liver during late hypoglycemic phase of sepsis. Si nce PKC-mediated phosphorylation plays an important role in regulating hepatic glucose metabolism, an inactivation of cytosolic PKC may cont ribute to the development of hypoglycemia during late phase of sepsis.