Myristic acid, unlike palmitic acid, is rapidly metabolized in cultured rat hepatocytes

This study was designed to examine and compare the metabolism of myristic a nd palmitic acids in cultured rat hepatocytes. [1-C-14]-Labeled fatty acids were solubilized with albumin at 0.1 mmol/L in culture medium. Incubation with 24-hr cultured hepatocytes was carried out for 12 hr. Myristic acid wa s mmol/L in culture (P < 0.05) taken up by the cells than was palmitic acid (86.9 +/- 0.9% and 68.3 +/- 5.7%, respectively, of the initial radioactivi ty was cleared from the medium after 4 hr incubation.) Incorporation into c ellular lipids, however, was similar after the same time (33.4 +/- 2.8% and 34.9 +/- 9.3%, respectively, of initial radioactivity). In the early phase of the incubation (30 min), myristic acid was more rapidly incorporated in to cellular triglycerides than was palmitic acid (7.4 +/- 0.9% and 3.6 +/- 1.9%, respectively, of initial radioactivity). However, after 12 hr incubat ion, the radioactivity of cellular triglycerides, cellular phospholipids, a nd secreted triglycerides was significantly higher with palmitic acid as pr ecursor. Myristic acid oxidation was significantly higher than that of palm itic acid (14.9 +/- 2.2% and 2.3 +/- 0.6%, respectively of the initial radi oactivity was incorporated into the beta-oxidation products after 4 hr). My ristic acid was also more strongly elongated to radiolabeled palmitic acid (12.2 +/- 0.8% of initial radioactivity after 12 hr) than palmitic acid was to stearic acid (5.1 +/- 1.3% of initial radioactivity after 12 hr). The c ombination of elongation and beta-oxidation results in the rapid disappeara nce of C14:0 in hepatocytes whereas C16:0 is esterified to form glycerolipi ds. This study provides evidence that myristic acid is more rapidly metabol ized in cultured hepatocytes than is palmitic acid. (C) Elsevier Science In c. 2000. All rights reserved.