Calcium transport by rat liver plasma membranes during sepsis

The effects of sepsis on the ATP-dependent Ca²⁺ transport in rat liver plasma membranes were investigated. Sepsis was induced by cecal ligation and puncture (CLP). Control rats were sham-operated. The results show that the ATP-dependent Ca²⁺ transport by liver plasma membranes was not affected during early sepsis (9 hr after CLP) but was decreased by 30-50% (P < 0.05) during late sepsis (18 hr after CLP). Kinetic analysis of the data indicates that during late sepsis, the Vmax values for ATP and for Ca²⁺ were decreased by 38.5% (P < 0.05) and 41.8% (P < 0.05), respectively, while the K(m) values for ATP and Ca²⁺ remained unchanged. Mg²⁺ stimulated ATP- dependent Ca²⁺ transport. The Mg²⁺-stimulated activity was unaffected during early sepsis but was decreased by 34-63% (P < 0.05) during late sepsis. These data demonstrate that ATP-dependent Ca²⁺ transport in rat liver plasma membranes was impaired during late sepsis and that the impairment is associated with a mechanism not affecting the affinity of the Ca²⁺ transporter for ATP and Ca²⁺. Since plasma membrane ATP-dependent Ca²⁺ transport plays an important role in the regulation of intracellular Ca²⁺ homeostasis in hepatocytes, an impairment in the ATP-dependent Ca²⁺ transport by liver plasma membranes during late sepsis may have a pathophysiological significance in contributing to the development of altered hepatic metabolism during septic shock.