Evaluation of purine nucleoside phosphorylase release as a measure of hepatic endothelial cell injury

Authors

  • Clifford A. Brass MD, PhD,

    Corresponding author
    1. Division of Gastroenterology, Department of Medicine, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, and the Philadelphia Veterans Administration Hospital, Philadelphia, PA
    • Division of Gastroenterology, University of Pennsylvania, CRB 638B. 422 Curie Blvd, Philadelphia, PA 19104-6144
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  • Milan G. Mody

    1. Division of Gastroenterology, Department of Medicine, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, and the Philadelphia Veterans Administration Hospital, Philadelphia, PA
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Abstract

With emerging data that endothelial cell (EC) injury is the limiting factor in liver preservation and hepatic function, a simple and reliable biochemical technique for monitoring EC injury is needed. Measurement of purine nucleoside phosphorylase (PNP) release into the circulation from perfused liver has been proposed as such a method. However, our experiments with perfused rat liver did not display a clear or direct relationship between PNP release and endothelial cell injury. Therefore, we re-examined the suitability of using PNP as a measure of nonparenchymal injury by measuring its distribution in purified populations of hepatocytes, ECs, and Kupffer cells (KCs) and correlating cell injury and enzyme release in short-term cultures at 37±C of each cell type. Purified cells were incubated (4 × 106 cells/mL) in oxygen or nitrogen saturated Wisconsin solution or Krebs buffer for 6 hours, with cell viability and PNP release assayed every 2 hours. ECs had the lowest specific activity (27 ± 9 U/mg protein; mean ± standard error of the mean [SEM]) compared with both hepatocytes (115 ± 15) and KCs (66 ± 18). Despite a decrement in EC and KC viability over time in each incubation solution, there was poor correlation between time of incubation and PNP release (r = 0.01 to 0.22), and between cell viability and PNP release (r = 0.01 to 0.16). In contrast, PNP release from incubated hepatocytes correlated with the length of incubation (r = 0.57 to 0.78) as well as cell injury (r = 0.63 to 0.77) in all four test solutions. This data suggest that PNP release is unlikely to specifically reflect EC injury in the intact liver. (Hepatology 1995;21:174–179).

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