EFFECTS OF THYROID-HORMONES, PHORBOL ESTERS, AND SPHINGOSINE ON THE INCORPORATION OF LINOLEIC-ACID INTO LIPIDS IN THE LIVER OF WHITE-RATS

Effects of thyroxine, phorbol esters, and sphingosine on the incorpora tion of [C-14]linoleic acid into endogenous phospholipids, triacylglyc erols, and cholesterol esters in the liver of white rats were studied. Phorbol 12-myristate 13-acetate and thyroxine activated the incorpora tion of [C-14]linoleic acid into endogenous phospholipids and triacylg lycerols in liver cells. However, phorbol 12-myristate 13-acetate 4-O- methyl ether had no effect, and methimazole and sphingosine suppressed the incorporation of fatty acids into glycerolipids in liver. The lat ter abolished the activating effect of thyroxine on this process. Sphi ngosine, thyroxine, and phorbol 12-myristate 13-acetate 4-O-methyl eth er did not affect the synthesis of cholesterol esters, but phorbol 12- myristate 13-acetate increased this process twofold in liver cells.