Alterations in Hepatic Gluconeogenesis, Prostanoid, and Intracellular Calcium during Sepsis

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Abstract
Objective: The metabolic alterations observed during sepsis may be associated with changes in local concentrations of intracellular calcium (Ca2+) and prostanoid synthesis in the liver. The authors studied hepatocyte intracellular Ca2+ and the release of glucose and prostanoid in an in‐vivo murine liver perfusion model. Methods: Sepsis was induced in anesthetized, fasted rats by cecal ligation and puncture (CLP, n = 42). Hepatic glucose release was studied in control (n = 10) and CLP (n = 10) groups using a non‐recirculating liver perfusion model with and without lactate as gluconeogenic substrate. Hepatocyte intracellular Ca2+ (n = 11) was measured using the selective indicator Fura‐2 under basal and epinephrine (10‐5 M) stimulated conditions. 6‐Keto‐prostaglandin F1α (6‐Keto) and thromboxane B2 (TxB2) were determined from liver perfusate by radioimmunassay (n = 11). Data were analyzed using t‐tests and repeated‐measures ANOVA. Results: Plasma glucose was significantly lower in CLP groups compared with controls (74.9 ± 6.6 vs 115.7 ± 4.6 mg/dL, p < 0.05). Plasma lactate was significantly higher in CLP vs controls (3.7 ± 0.4 vs 1.4 ± 0.1 mM, p < 0.05). Glucose release in isolated perfused livers was significantly lower in CLP vs controls (8.5 vs 16 ± 1.2 μM/g/hr, p < 0.001). With the addition of lactate + pyruvate to the perfusate, glucose output in CLP livers was significantly lower following 5 (9.9 ± 0.7 vs 17.7 ± 1.1 μM/g/hr, p < 0.05) and 10 (11.9 ± 1.2 vs 20.6 ± 1.3 μM/g/hr, p < 0.001) minutes of perfusion. The basal level of intracellular calcium ([Ca2+]i) in CLP rats (460.1 ± 91.6 nM) was significantly higher than in control rats (196.3 ± 35.5 nM) (p < 0.05). A significant increase (p < 0.05) in [Ca2+]i occurred after the addition of epinephrine in hepatocytes in control (196.3 ± 35.5 vs 331.8 ± 41.4 nM) but not CLP (460.1 ± 91.6 vs 489.4 ± 105 nM) rats. 6‐Keto was significantly lower in CLP compared with controls at 30 minutes (25.7 ± 3.9 vs 33.4 ± 5.5 pg/mL, p < 0.05), whereas TxB2 was not significantly altered (52.1 ± 34.7 vs 87.5 ± 43.2 pg/mL). Conclusion: These results demonstrate that CLP sepsis is associated with an increase in hepatocyte intracellular free Ca2+ concentration along with attenuation of hormone‐mediated Ca2+ mobilization and hepatic gluconeogenesis.