Metabolism of ether-linked glycerolipids in cultures of normal and neoplastic rat respiratory tract epithelium.

Abstract

To study the mechanism of ether lipid accumulation which is characteristic of many tumors, we have compared the metabolism of lipids in primary rat tracheal epithelial cells and in a cell line derived from a benzo(a)pyrene-induced tumor. Growth of the primary epithelial cells in vitro resulted in the accumulation of alkyldiacylglycerols at levels (10% of total lipid) comparable to those found in the tumor cell line (B2-1). This class of ether lipids could not be detected in normal rat tracheal epithelium in vivo. A double isotope labeling method using (/sup 3/H)- and (/sup 14/C)palmatic acid was used to study metabolic stability of lipid classes in the cell cultures. Primary cells and B2-1 cells labeled with palmitic acid showed the greatest loss of label from triacylglycerols and free fatty acids during incubation in unlabeled media. A slight loss of label from the ester linkages of the alkyldiacylglycerols was observed in the primary epithelial cells but not the B2-1 cells. No label was lost from the ether linages of the alkyldiacylglycerols of either the B2-1 or primary cells. With the exception of diradlglycerophosphocholine, phospholipids of primary and B2-1 cells labeled with palmitic acid accumulated label during incubation in unlabeled media. Similar resultsmore » were observed with the B2-1 cells using labeled glycerol as the lipid precursor. The results demonstrate that alkyldiacylglycerols can be induced in nontumorigenic cells by growth in culture and can thus provide a useful model for studying the regulation of ether lipid metabolism.« less