Ray Manning

Early effects of oestrogen treatment on lipogenesis de novo and on biosynthesis of triacylglycerol from fatty acids in male chick liver

1. Early changes (0-44 hr) in liver and plasma lipid levels and in the rate of hepatic lipogenesis were measured in male chicks after a single intramuscular injection of oestradiol-17 beta. 2. Chick liver slices were employed to measure the rate of lipogenesis de novo using 3H2O and the rate of triacylglycerol synthesis from [9, 10-3H] palmitate at various times after injection. 3. The results suggest that oestrogen-induced lipogenesis occurs initially by a rapid and coordinated stimulation of the total hepatic capacity for lipogenesis de novo and for triacyglycerol synthesis from fatty acids. 4. The results are discussed in relation to oestrogen-induced changes in hepatic lipogenic enzymes.

Temporal changes in plasma and liver lipids and in the hepatic activities of acetyl-coenzyme a carboxylase and fatty acid synthetase after oestrogen treatment of the male chicken (gallus domesticus)

1. Male chickens (Gallus domesticus) were treated with a single intramuscular injection of oestradiol-17 beta, then changes in the liver and plasma levels of triacylglycerol, phospholipid, nonesterified fatty acids and in the hepatic activities of acetyl-CoA carboxylase and fatty acid synthetase were measured at various times after injection. 2. The results suggest that the initial phase (less than 20 hr) of oestrogen-induced hyperlipidaemia occurs in the absence of changes in the hepatic activities of the major enzymes of fatty acid biosynthesis, but a subsequent increase in these enzyme activities may contribute to the later phase (greater than 20 hr) of oestrogen-induced lipogenesis in avian liver.

LIPID CHANGES IN HL-60 CELLS ON DIFFERENTIATION INTO MACROPHAGES BY TREATMENT WITH A PHORBOL ESTER

We studied changes in lipid composition of human promyelocytic leukemia cells (HL-60) on differentiation to the macrophage/monocytic lineage by treatment with the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate. Differentiation was accompanied by: (i) a decrease in the level of phospholipids; (ii) a greater amount of triacylglycerols; (iii) an increase in 1-alk-1′-enyl-2-acyl- and 1-alkyl-2-acyl-sn-glycero-3-phosphoethanolamine and a decrease in 1-alkyl-2-acyl-sn-glycero-3-phosphocholine; and (iv) an increase in the level of arachidonic acid in ethanolamine phospholipids. The increased levels of ether-linked lipids and of arachidonic acid in ethanolamine phospholipids are consistent with an enhanced biosynthesis of platelet-activating factor and eicosanoids, which are particularly important in the macrophage function.

Effect of dietary modulation of membrane lipid composition on the thermostability of HTC cells and of a membrane enzyme

Growth of hepatoma tissue culture (HTC) cells in the presence of linoleic (18:2) or arachidonic (20:4) acids for 36 h caused an increased cell thermosensitivity. Plasma membrane-rich fractions were purified (15-20-fold) with high yield (30%) from control and fatty acid-supplemented cells. Contamination with membranes from mitochondria, lysosomes and endoplasmic reticulum was low. Supplementation significantly increased the level of the supplemented fatty acid and decreased the level of oleic acid (18:1) in plasma membrane phospholipids (PL), causing a significant decrease in the oleic acid:PUFA (polyunsaturated fatty acid) ratio. No significant changes occurred in other parameters such as cholesterol:PL, cholesterol:protein or PL:protein ratios. Plasma membranes from PUFA-supplemented cells exhibited a lower membrane order, compared with control cell membranes, as determined by DPH fluorescence polarization over the temperature range 4-40 degrees C. Isothermal inactivation of alkaline phosphodiesterase I in plasma membranes from control and supplemented cells showed curvilinear kinetics. The change in membrane composition and order following supplementation with arachidonic acid was associated with increased thermosensitivity of this enzyme. These data are discussed with respect to the suggestion that the plasma membrane may be a target for cellular thermal injury and death.

Glucose kinetics in the oestrogen-treated male chicken (Gallus domesticus), measured after administration of [6-3H]glucose and [U-14C]glucose in vivo

Male chickens (Gallus domesticus) were treated with 17 beta-oestradiol then injected with a mixture of [6-3H]glucose and [U-14C]glucose. Subsequently, blood samples were taken to determine plasma lipid levels and several parameters of glucose metabolism, including entry rate, carbon recycling, mean transit time, the total body glucose mass, the mass of the sampling pool and the rate of outflow from this pool. Oestrogen-treated birds exhibited typical hyperlipidaemia, with significantly elevated plasma levels of triacylglyerol and nonesterified fatty acids. Oestrogen administration significantly decreased the glucose entry rate, the total body glucose mass and the rate of outflow from the sampling pool.