Primed pentose cycle activity supports production and elimination of superoxide anion in Kupffer cells from rats treated with endotoxin in vivo

Glucose use and pentose cycle activity were determined in freshly isolated rat Kupffer cells 3 h after an i.v. injection of Escherichia coli endotoxin (0.1 mg/kg body weight), by using [1-¹⁴C], [6-¹⁴C] and [2-³H]glucose. Endotoxin treatment in vivo caused a 5-fold increase in the basal glucose uptake in Kupffer cells. Pentose cycle activity was elevated from 8.7 to 13.6 nmol/h per 10⁷ cells after endotoxin. In vitro treatment of the cells from saline- and endotoxin-treated animals with phorbol ester (10^-6 M) increased pentose cycle activity 2-fold and 8-fold, respectively. Phorbol ester caused a 50% increase in glucose uptake in both groups. t-Butyl hydroperoxide (0.5 mM) caused a similar increase in pentose cycle activity as phorbol ester. Glucose oxidation in the Krebs cycle was also doubled after endotoxin. KC from endotoxin-treated animals produced O^-₂ spontaneously, and were primed to produce additional large amounts of O^-₂ upon phorbol ester treatment. Addition of t-butyl hydroperoxide inhibited O^-₂ production by Kupffer cells. Depletion of glutathione by N-ethylmaleimide (0.1 mM), or inhibition of NADPH oxidase by diphenyliodonium (0.1 mM) inhibited both the pentose cycle activity and the O^-₂ production. Increasing the concentration of exogenous glucose in the cell medium elevated the glycolytic rate, while pentose cycle flux was not affected either under basal conditions or following subsequent challenges by phorbol ester or t-butyl hydroperoxide. Our data suggest that the endotoxin-induced elevated glucose use in Kupffer cells is accompanied by a primed state of the pentose cycle. This condition supports superoxide and macromolecule synthesis and could also represent a potentiated protective mechanism against oxidative cellular injury during bacterial infections.