Synthesis of fatty acid synthetase by isolated liver cells obtained from rats in different nutritional or hormonal states

Abstract

Parenchymal cells from livers of rats in different nutritional and hormonal states were isolated by perfusion with calcium-free, glucose-free Hanks' solution containing 0.05% collagenase and 0.10% hyaluronidase. The ability of these cells to synthesize the fatty acid synthetase complex was then studied. Liver cells isolated from animals refed a fat-free diet for 16 hr following a 48-hr period of fasting incorporated l-[U- 14C] leucine into fatty acid synthetase at a rate 16.2 times faster than cells isolated from livers of animals fed a normal diet. The ratio of incorporation of label into fatty acid synthetase to incorporation into total cellular protein by the cells from refed animals was 17.9-fold greater than that of cells from normal animals. This result is consistent with our previous in vivo studies on the synthesis of the enzyme complex [Craig, M. C., Nepokroeff, C. M., Lakshmanan, M. R., and Porter, J. W. (1972) Arch. Biochem. Biophys. 152, 619–630] in which the rate of synthesis of fatty acid synthetase relative to overall soluble protein synthesis in animals fasted and then refed a fat-free diet for 72 hr was 14.3 times the value obtained for normal animals. Cells from fasted or diabetic animals incorporated radioactive leucine into fatty acid synthetase at a rate 0.34 or 0.11, respectively, of the rate in cells from normal animals. However, this difference in incorporation of radioactivity by cells from diabetic or fasted animals compared to normal cells was not observed when determinations were made of the incorporation of label into fatty acid synthetase relative to incorporation of label into overall cellular protein.