Accumulation of diacylglycerol in the liver membrane of the Long-Evans Cinnamon (LEC) rat with hepatitis: FT-IR spectroscopic and HPLC detection

Long-Evans Cinnamon (LEC) rats develop severe hepatitis and subsequent hepatoma with excess accumulation of copper in the liver with increasing age. Lipids extracted from the LEC rat liver membrane were studied using FT-IR spectroscopy and an HPLC technique at the stages of pre-hepatitis and hepatitis, i.e. at 10 and 16 weeks of age, respectively. The 10-week-old rats exhibited an IR spectrum characteristic of a phosphatidylcholine and phosphatidylethanolamine mixture with a ratio of 2:1. The 16-week-old rats developed new absorption bands at 1161 and 1070 cm−1, which were assigned to the spectra of triglyceride, neutral lipid, and diacylglycerol, an endogenous activator of protein kinase C, respectively. The diacylglycerol was estimated to amount to ca. 10% (w/w) of phospholipid extract by comparing the spectrum with those of model compounds. This was confirmed using an HPLC assay. Previously, we found that a serum response factor is activated by copper in the LEC rat liver, and suggested that it must mediate proto-oncogene c-fos induction. The results obtained here suggest that accumulation of diacylglycerol plays an important role in development of hepatoma in LEC rats by mediating proto-oncogene c-fos induction.