STEARIC-ACID UNLIKE SHORTER-CHAIN SATURATED FATTY-ACIDS IS POORLY UTILIZED FOR TRIACYLGLYCEROL SYNTHESIS AND BETA-OXIDATION IN CULTURED RATHEPATOCYTES

Utilization of stearate as compared to various saturated fatty acids f or cholesterol and lipid synthesis and beta-oxidation was determined i n primary culture of rat hepatocytes. At 0.5 mmol/L in the medium, ste arate (18:0) adequately solubilized by albumin was less inhibitory to cholesterol synthesis from [2-C-14] acetate than myristate (14:0) and palmitate (16:0) (68% vs. 91 and 88% inhibition, respectively). The ra te of incorporation into cholesterol from [1-C-14] stearate (3.0 +/- 0 .6 nmol/mg protein/4 h) was 37-, 1.8-, and 7.8-fold of that from myris tate, palmitate, and oleate, respectively. Conversely, the rate of [1- C-14] stearate incorporation into total glycerolipids was 88-90% lower than that of labeled palmitate, myristate, and oleate. The rate of [1 -C-14] stearate incorporation into triacylglycerol (3.6 +/- 0.4 nmol/m g protein/4 h) was 6-8% of that from myristate, palmitate, oleate, and linoleate. The rate of stearate incorporation into phospholipids was the lowest among tested fatty acids, whereas the rate of mono-and diac ylglycerol synthesis was the highest with stearate treatment. The rate of beta-oxidation as measured by CO2 and acid soluble metabolite prod uction was also the lowest with [1-C-14] stearate treatment at 22.7 nm ol/mg protein/4 h, which was 35-40% of those from other [1-C-14] label ed fatty acids. A greater proportion of stearate than other fatty acid s taken up by the hepatocytes remained free and was not metabolized. C learly, stearate as compared to shorter-chain saturated fatty acids wa s less efficiently oxidized and esterified to triacylglycerol in cultu red rat hepatocytes.