Background. We recently demonstrated that pancreatitis-associated ascitic fluid (PAAF) contains cytotoxic factor(s), inducing apoptosis in hepatocytes, and that PAAF induces hepatic adenosine triphosphate depletion, hepatocellular acidosis, and accumulation of hepatic intracellular sodium. Because ascitic fluid and serum from patients with hemorrhagic pancreatitis contain a lot of hematin, we aimed to test the hypothesis that hematin can induce hepatocellular injury, and then we compared its cytotoxicity with that of PAAF. Methods. In vivo effects of intraperitoneal injection of hematin into the liver of healthy rats were evaluated with in situ nick-end labeling, blood biochemical analysis, and nuclear magnetic resonance spectroscopy. In vitro cytotoxic and apoptosis-inducing activities of hematin on rat primary culture hepatocytes were investigated with a cellular proliferation assay kit and DNA fragmentation enzyme-linked immunosorbent assay, respectively. Furthermore, PAAF was fractionated with Sephacryl S-300 gel column chromatography, and cytotoxic activities of its fractions on a human hepatoma cell line (HuH-7) were compared with those of hematin. Results. Intraperitoneal injection of hematin into healthy rats caused apoptosis in the hepatocytes and elevated serum glutamate oxaloacetic transaminase and lactate dehydrogenase levels. Intraperitoneal injection of hematin also caused a significant decrease in the hepatic β-adenosine triphosphate/inorganic phosphate ratio, severe hepatic intracellular acidosis, and a significant increase of hepatic intracellular sodium (Na+) concentration, similar to the effects of PAAF. In vitro, hematin decreased hepatocyte viability and increased the DNA fragmentation of hepatocytes, similar to the effects of 10% PAAF. Albumin reversed the cytotoxic effects of hematin and PAAF on HuH-7 cells nearly completely and partially, respectively. Fractionation of PAAF and hematin by gel column chromatography revealed that the first peak of cytotoxic activity of PAAF corresponded to that of hematin and that the cytotoxic activity was reversed by albumin nearly completely. Conclusions. These results suggest that hematin is one of the cytotoxic factors in PAAF that causes hepatocellular injury and that cellular injuries caused by hematin may be involved in the development of multiple organ failure associated with severe acute pancreatitis.
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