DISSOCIATION OF PROTEIN-KINASE-C ACTIVITIES AND DIACYLGLYCEROL LEVELSIN LIVER PLASMA-MEMBRANES OF RATS ON COCONUT OIL AND SAFFLOWER OIL DIETS

The activation of protein kinase C (PKC) is affected differently in vi tro by different fatty acids. Whether this event occurs in response to fatty acid has not heretofore been determined in animal tissues. We a ddressed this question using the liver of rats on diets containing sat urated or polyunsaturated fats. Rats on coconut oil, which is rich in saturated fatty acids, had a markedly lower PKC activity in liver plas ma membranes with a slight but significant reduction of the activity i n the cytosol than did rats fed safflower oil rich in linoleic acid. I ngestion of coconut oil resulted in a higher content of diacylglycerol s (DG) in these membranes than did ingestion of safflower oil, whereas the proportions of saturated fatty acids and phospholipids and membra ne fluidity were similar between rats ingesting different fats. These results are the first evidence that ingestion of coconut oil dispropor tionately affects PKC activation and the DG level in mammalian membran es. It seems likely that saturated fats exert various physiological ef fects on lipid and lipoprotein metabolism, in parr through PKC pathway s.