Time course of incorporation of 20-carbon polyunsaturated fatty acids in a human keratinocyte cell line

Chain separation of monounsaturated fatty acid methyl esters by argentation thin-layer chromatography

A technique for separating methyl esters of monounsaturated fatty acids by argentation chromatography using silver nitrate-impregnated TLC plates is described. Monounsaturated fatty acid methyl esters are separated from polyunsaturated and saturated fatty acid methyl esters and the monounsaturated fatty methyl esters are resolved according to chain length. cis isomers are well resolved from the corresponding trans isomers. R(F) values for individual monounsaturated fatty acids are very reproducible. The potential of the technique in metabolic studies is demonstrated in the chain elongation of [14C]-18:1(n-9) and delta-9 desaturation of [14C]-18:0 by human skin fibroblasts. Recoveries of individual [14C]-fatty acids for scintillation counting exceed 94%.

Arachidonic acid and human bone marrow stromal cells

Human bone marrow stromal cells regulate the growth of marrow hematopoietic progenitors by secreting cytokines. Arachidonic acid (AA) is the fatty acid precursor of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) that modulate the growth of human bone marrow progenitors. We have investigated the incorporation of AA in human bone marrow stromal cell cultures, their production of PGE2 and LTB4 and the effect of AA on their growth. Gas chromatography analysis reveals the presence of AA in the human bone marrow plasma and in bone marrow stromal cell cultures. In stromal cells, [3H]-AA is incorporated into triglycerides and is later delivered into phospholipids. Prelabeling-chase experiments indicate a preferential incorporation of AA into phosphatidylethanolamine and no trafficking of labeled AA between phospholipid species. Bone marrow stromal cells release PGE2 and LTB4 in response to phorbol myristic acetate (PMA) (1 microM) and tumor necrosis factor alpha (TNF-alpha) (10 ng/ml). Exogenous AA (up to 1 microM) has no significant effect on cell growth. In conclusion, human bone marrow stromal cells capt exogenous AA and, thus, may participate to the control of marrow AA concentrations. They may also regulate human marrow hematopoiesis by secreting AA metabolites such as PGE2 and LTB4.

Incorporation of arachidonic acid in a human cancer gastric tumor cell line (HGT) at various stages of cell proliferation

Human cancer gastric cells (HGT) in culture were labeled with [14C]arachidonic acid. The kinetic of acylation of arachidonic acid was similar using cells after 3, 5 and 7 days of culture. However, the duration of the proliferation enhanced the acyltransfer to triglycerides and inhibited the transfer to phospholipids. After 8 h of incubation with [14C]arachidonic acid the radioactivity was predominantly recovered in the phosphatidylcholine and phosphatidylethanolamine species. Prelabeling-chase experiments indicated a preferential incorporation of arachidonic acid into phosphatidylcholine followed by a transfer of arachidonate to phosphatidylethanolamine.

Incorporation of arachidonic, dihomogamma linolenic and eicosapentaenoic acids into cultured V79 cells

The uptake and distribution of three common dietary polyunsaturated fatty acids was studied using Chinese hamster lung fibroblasts (V79 cells). Treatment of V79 cells with arachidonic (20:4), eicosapentaenoic (20:5) and dihomogammalinolenic (20.3) acids for 24 hr produced a marked uptake of 20:3 and 20:4, both of which were assimilated to a considerably greater degree than 20:5. All polyunsaturated fatty acids were incorporated primarily into phospholipids; however, there were considerable differences in their distribution into individual phospholipid species. Although 20:4 was incorporated primarily into phosphatidylcholine, 20:3 entered largely into phosphatidylethanolamine and phosphatidylglycerol, and 20:5 was distributed about equally between phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol. A marked conversion of 20:3 to 20:4 was found after 24 hr and, in several phospholipids, there was as much derived-radiolabeled 20:4 as there was radiolabeled 20:3. There was little evidence of 20:4 and 20:5 metabolism. V79 cells undergo substantial changes in phospholipid fatty acid composition following supplementation with these polyunsaturated fatty acids; however, these fatty acids are assimilated to different degrees and their distribution among cellular phospholipids is distinct, suggesting incorporation via independent mechanisms.

Incorporation and distribution of eicosanoid precursor fatty acids in murine fibroblasts in culture

Murine fibroblasts in culture were labelled with either [14C]arachidonic acid, [14C]dihomo-gamma-linolenic acid or [14C]eicosapentaenoic acid. All these [14C]fatty acids were effectively incorporated into the fibroblasts and the bulk of the radioactivity was recovered in various phospholipids. The major radiolabelled phospholipids were phosphatidylethanolamine, phosphatidylcholine and the phosphatidylinositol + phosphatidylserine fraction. Significant amounts of radiolabel were found also in the triacylglycerols: even as much as 30% of the total of the incorporated dihomo-gamma-linolenic acid was recovered in the triacylglycerols. The present study suggests that arachidonic acid, dihomo-gamma-linolenic acid and eicosapentaenoic acid are effectively taken up and esterified into different lipid fractions of murine fibroblasts and that also the triacylglycerols are significantly involved in the incorporation, storage, and release of the eicosanoid precursor fatty acids.