In this study, we tested the hypothesis that dietary
linoleic acid intake controls the arterial blood plasma
linoleic acid concentration and the rates of
tumor growth and
linoleic acid metabolism in vivo. Seven groups of young male Buffalo rats (11-21 rats/group) were given free access to semipurified diets containing different amounts of corn and/or
olive oils. Four other groups (7-11 rats/group) were 30% energy-restricted. Each experiment included periods for rat growth and plasma
lipid stabilization (6 wk), measurement of mean daily arterial blood plasma
fatty acid concentrations (3 wk), surgical implantation of a subcutaneous tissue-isolated
hepatoma 7288CTC,
tumor growth and harvest (2-4 wk). Linoleic +
arachidonic acid (P = 0.007) and
oleic acid (P = 0.002) concentrations in arterial blood plasma were increased as dietary intake of linoleic and
oleic acids was increased, respectively. In rats given free access to food,
tumor growth was directly dependent on the plasma concentrations of linoleic (P < 0.001) and
arachidonic acids (P = 0.04).
Tumor growth in energy-restricted rats was dependent only on the
linoleic acid concentration (P = 0.008). Energy restriction itself caused a growth inhibition independent of plasma
linoleic acid. The
linoleic acid and total
fatty acid concentrations of
tumor triacylglycerols were directly dependent on the plasma
linoleic acid concentration in rats given free access to food (P = 0.009).
Hepatoma 7288CTC (both in vivo and during perfusion in situ) supported a dose-dependent conversion (P < 0.001) of plasma
linoleic acid to the
mitogen, 13-hydroxy-9, 11-octadecadienoic
acid. We conclude that increased arterial blood plasma
linoleic acid concentrations, caused by increased dietary intakes, specifically stimulate growth,
lipid storage and
linoleic acid metabolism in
hepatoma 7288CTC in vivo.