High intracellular 1,2,-sn-diacylglycerol (DAG) usually activates
protein kinase C (PKC). In
choline-deficient Fischer 344 rats, we previously showed that
fatty liver was associated with elevated hepatic DAG and sustained activation of PKC. Steatosis is a sequelae of many liver toxins, and we wanted to determine whether
fatty liver is always associated with accumulation of DAG with activation of PKC. Obese Zucker rats had 11-fold more
triacylglycerol in their livers and 2-fold more DAG in their hepatic plasma membrane than did lean control Zucker rats. However, this increased
diacylglycerol was not associated with translocation or activation of PKC in hepatic plasma membrane (activity in obese rats was 897 pmol/mg
protein X min(-1) vs. 780 pmol/mg
protein X min(-1) in lean rats). No differences in PKC
isoform expression were detected between obese and lean rats. In additional studies, we found that
choline deficiency in the Zucker rat did not result in activation of PKC in liver, unlike our earlier observations in the
choline deficient Fischer rat. This dissociation between
fatty liver, DAG accumulation and PKC activation in Zucker rats supports previous reports of abnormalities in PKC signaling in this strain of rats.