Membrane lipids of hepatic tissue. I. Neutral lipids from subcellular fractions of liver and hepatoma 7288CTC

Abstract

Enriched subcellular fractions of nuclei, mitochondria, endoplasmic reticulum (ER), plasma membrane, and cytosol were prepared from liver and hepatoma 7288CTC taken from male inbred BUF rats. Purity was established by marker enzyme activities and distribution of DNA, RNA, sialic acids, total phospholipids, and cholesterol. The subcellular fractions of hepatoma differed from those of liver: 5'-Nucleotidase activity was elevated in ER and mitochondria, cytosol RNA was increased, and cholesterol was elevated in all hepatoma subcellular fractions. Neutral lipid classes of hepatoma subcellular fractions differed quantitatively from those of liver: Hepatoma nuclei and mitochondria contained elevated levels of free fatty acids (FFA) and triglycerides (TG). Generally, the fatty acid profiles of FFA, TG, and sterol esters from hepatoma subcellular fractions were more uniform and showed less organelle specificity than did liver. Hepatoma FFA and TG contained lower percentages of palmitate and higher percentages of stearate in all subcellular fractions than did liver. The sterol esters from most hepatoma subcellular fractions compared to those from liver were characterized by much higher levels of long-chain fatty acids of 20 carbon atoms or longer. The oleate-to-vaccenate ratio in FFA of liver subcellular fractions exhibited some specificity, but not that of hepatoma subcellular fractions. The oleate-to-vaccenate ratio in the acyl chains of liver and hepatoma TG did not reveal organelle specificity.