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Journal of Lipid Research, Vol. 15, 309-316, July 1974
Copyright © 1974 by Lipid Research, Inc.

Utilization of ascites plasma very low density lipoprotein triglycerides by Ehrlich cells

Douglas E. Brenneman and Arthur A. Spector

Departments of Biochemistry and Internal Medicine, University of Iowa, Iowa City, Iowa 52242

Much of the lipid present in the ascites plasma in which Ehrlich cells grow is contained in very low density lipoproteins (VLDL). Chemical measurements indicated that triglycerides were taken up by the cells during in vitro incubation with ascites VLDL. When tracer amounts of radioactive triolein were incorporated into the ascites VLDL, the percentage uptakes of glyceryl tri[1-¹⁴C]oleate and triglycerides measured chemically were similar. The cells also took up [2-³H]glyceryl trioleate that was added to VLDL, but the percentage of available ³H recovered in the cell lipids was 30-40% less than that of ^{1 4}C from glyceryl tri[1-^{1 4}C]oleate. This difference was accounted for by water-soluble ³H that accumulated in the incubation medium, suggesting that extensive hydrolysis accompanied the uptake of VLDL triglycerides. Radioactive fatty acids derived from the VLDL triglycerides were incorporated into cell phospholipids, glycerides, and free fatty acids, and they also were oxidized to CO₂. Triglyceride utilization increased as the VLDL concentration was raised. These results suggest that one function of the ascites plasma VLDL may be to supply fatty acid to the Ehrlich cells and that the availability of fatty acid to this tumor is determined in part by the ascites plasma VLDL concentration. Although Ehrlich cells incorporate almost no free glycerol into triglycerides, considerable amounts of [2-³H]glyceryl trioleate radioactivity were recovered in cell triglycerides. This indicates that at least some VLDL triglycerides were taken up intact. The net uptake of VLDL protein and cholesterol was very small relative to the triglyceride uptake, suggesting that intact triglycerides are transferred from the ascites VLDL to the Ehrlich cells and that hydrolysis occurs after the triglyceride is associated with the cells.

Supplementary key words tumors • fatty acids • esterification • oxidation • hydrolysis • cholesterol

Submitted on April 30, 1973
Revised on November 26, 1973
Accepted on February 27, 1974

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