PROTEIN-KINASE-C ACTIVITY IS INCREASED IN RAT-HEART DURING THE EARLY HYPERDYNAMIC PHASE OF SEPSIS

Changes in protein kinase C (PKC) (calcium-and phosphotipid-dependent protein kinase) activity in rat heart during different cardiodynamic p hases of sepsis were studied in an attempt to understand the pathophys iology of altered myocardial function during sepsis. Sepsis was induce d by cecal ligation and puncture. Experiments were divided into three groups: control, early sepsis, and late sepsis. Early and late sepsis refers to those animals sacrificed at 9 and 18 h, respectively, after cecal ligation and puncture. Cardiac PKC was extracted and partially p urified by ammonium sulfate fractionation and diethylaminoethyl-cellul ose chromatography. PKC activity was assayed on the basis of the rate of incorporation of P-32 from [gamma-P-32]adenosine triphosphate into histone. The results show that during early sepsis, cytosolic PKC acti vity was increased by 42-73%, whereas membrane associated PKC activity was unchanged. During late sepsis, both cytosolic and membrane associ ated PKC activities remained unchanged. Kinetic analysis of the data o n cytosolic PKC during the early phase of sepsis reveals that the V-ma x (maximal velocity) values for Ca2+, phosphatidylserine, and diacylgl ycerol were increased by 58, 42, and 50%, respectively. with no change s in their K-m (substrate concentration required for half-maximal enzy me activity) values. These data indicate that cytosolic PKC activity w as activated in rat heart during the early hyperdynamic phase of sepsi s. Because PKC mediated phosphorylation plays an important role in reg ulating myocardial contractility, an activation in cytosolic PKC may c ontribute to the development of a hypercardiodynamic state during the early phase of sepsis.