EPIDERMAL GROWTH-FACTOR STIMULATES LINOLEIC-ACID METABOLISM IN BALB/C 3T3-FIBROBLASTS

Abstract

One response of BALB/c 3T3 cells to epidermal growth factor (EGF) is the release and subsequent metabolism of arachidonic acid. Prostaglandins generated from EGF treatment appear to play a role in the mitogenic signal. Lipoxygenase inhibitors (nordihydroguaiaretic acid and 5, 8, 11, 14-eicosatetraynoic acid) were previously shown to be very effective in blocking EGF-stimulated DNA synthesis; however, only low levels of lipoxygenase-derived arachidonate metabolites were detected. In an extension of these investigations, we have now found that EGF stimulates lipoxygenase metabolites of linoleic acid in BALB/c 3T3 fibroblasts. In the presence of EGF (10 ng/ml), the cells converted 10-15% of exogenous linoleic acid (10 .mu.M) to hydroxy fatty acids that were isolated on reverse phase high performance liquid chromatography. No linoleate metabolites were detected in the absence of EGF. The isolated compounds were characterized further by straight phase high performance liquid chromatography, UV spectroscopy, and gas chromatography-mass spectrometry analyses, and they were identified as 13-hydroxyoctadecadeienoic acid and 9-hydroxyoctadecadienoic acid. The hydroxy metabolites and their hydroperoxy precursors produced a 2- to 4-fold potentiation of EGF-stimulated [3H]thymidine incorporation in BALA/c 3T3 cells. These linoleate derivatives stimulated DNA synthesis at concentration ranges of 10-8 to 10-6 M. Thus, linoleic acid metabolism might be an important element in the EGF-regulated cascade of biochemical events leading to fibroblast mitogenesis.