Dissociation of protein kinase C activities and diacylglycerol levels in liver plasma membranes of rats on coconut oil and safflower oil diets

The activation of protein kinase C (PKC) is affected differently in vitro by different fatty acids. Whether this event occurs in response to fatty acid has not heretofore been determined in animal tissues. We addressed this question using the liver of rats on diets containing saturated or polyunsaturated fats. Rats on coconut oil, which is rich in saturated fatty acids, had a markedly lower PKC activity in liver plasma membranes with a slight but significant reduction of the activity in the cytosol than did rats fed safflower oil rich in linoleic acid. Ingestion of coconut oil resulted in a higher content of diacylglycerols (DG) in these membranes than did ingestion of safflower oil, whereas the proportions of saturated fatty acids and phospholipids and membrane fluidity were similar between rats ingesting different fats. These results are the first evidence that ingestion of coconut oil disproportionately affects PKC activation and the DG level in mammalian membranes. It seems likely that saturated fats exert various physiological effects on lipid and lipoprotein metabolism, in part through PKC pathways.