GTP-binding protein mediated phospholipase A2 activation in rat liver during the progression of sepsis

Effects of GTP-binding proteins on the activation of secretory phospholipaseA2 (sPLA2) and cytosolic phospholipaseA2 (cPLA2) in rat liver during two different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). 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 CLP. The results show that in the absence of G-protein modulator, hepatic sPLA2 and cPLA2 activities were activated by 40.8-46 and 91.6-105.8%, respectively, during early and late phases of sepsis. GTPgammaS and fluoroaluminate (AlF4-) stimulated sPLA2 and cPLA2 activities within each experimental group, i.e., control, early sepsis, and late sepsis. The GTPgammaS and AlF4(-)-stimulated sPLA2 and cPLA2 activities remained significantly elevated during early phase (22.3-65.6% increase) and late phase (32.5-109.1% increase) of sepsis. Further analyses demonstrate that cholera toxin significantly stimulated sPLA2 and cPLA2 activities within each experimental group, and that the cholera toxin stimulated sPLA2 and cPLA2 activities remained significantly higher during early phase (23.5-37% increase) and late phase (56.7-70% increase) of sepsis. In contrast, pertussis toxin significantly inhibited sPLA2 and cPLA2 activities within each experimental group, and that the pertussis toxin-inhibited sPLA2 and cPLA2 activities remained significantly higher in early septic (57-68.5% increase) and late septic (34.6-45.5% increase) experiments. These data demonstrate that cholera toxin-sensitive G alpha s and pertussis toxin-sensitive G alpha i were both involved in the activation of sPLA2 and cPLA2 activities in rat liver during the progression of sepsis.