Cold preservation-warm reoxygenation increases hepatocyte steady-state Ca2+ and response to Ca2+-mobilizing agonist

Although the role of Ca2+ in liver transplantation injury has been the object of several studies, direct evidence for alterations in intracellular Ca2+ homeostasis after cold preservation-warm reoxygenation (CP/WR) has never been presented. We thus investigated the effects of CP/WR on steady-state Ca2+ and responses to a Ca2+-mobilizing agonist. Isolated rat hepatocytes were suspended in University of Wisconsin solution, stored at 4 degreesC for 0, 24, and 48 h, and reoxygenated at 37 degreesC for 1 h. Cytosolic Ca2+ was measured in single cells by digitized fluorescence videomicroscopy. CP/WR caused a significant increase in steady-state cytosolic Ca2+, which was inversely proportional to cell viability. Pretreatment of hepatocytes with an agent that protects mitochondrial function attenuated the increase in steady-state cytosolic Ca2+ and improved hepatocyte viability. Ca2+ responses to the purinergic agonist ATP also increased significantly as a. function of cold storage time. This increase was related to an increase in the size of inositol 1,4,5-trisphosphate-sensitive Ca2+ stores and subsequent capacitative Ca2+ entry. Thus CP/WR significantly perturbs steady-state hepatocellular Ca2+ and responses to Ca2+-mobilizing agonists, which may contribute to hepatocyte metabolic dysfunction observed after CP/WR.