Lipid composition of erythrocytes and thrombocytes of a subantarctic seabird, the king penguin.

Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n-3 polyunsaturated FA. Results were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other birds, cardiolipin levels were unexpectedly high (4%). Very long chain n-3 FA were abundant (13-27%) in phosphatidylethanolamine (PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n-3 FA, 22:6n-3 was the most abundant in all PL (2-20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels of n-3 FA (9-12%) were 1.5-2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%). The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of avian thrombocytes and erythrocytes.

Lipid composition of blood platelets and erythrocytes of southern elephant seal (Mirounga leonina) and antarctic fur seal (Arctocephalus gazella).

Erythrocyte and blood platelet phospholipid compositions were studied in three elephant seals and two fur seals, two species of marine mammals living in the Subantarctic region feeding on preys rich in (n-3) polyunsaturated fatty acids. Results were compared with those reported for related species and humans. In erythrocytes, the phospholipid (PL) and cholesterol (CHOL) contents were lower in pinnipeds than in humans. Phosphatidylcholine (PC) levels were higher in elephant seals than in fur seals, with a reverse trend for phosphatidylethanolamine (PE) and phosphatidylserine (PS). Both species had lower SM/PC ratios and PE plasmalogen concentrations than human. Erythrocytes were richer in (n-3) fatty acids (FA) in pinnipeds than in humans. In platelets, the PL content was lower and the CHOL content higher in elephant seals than in humans or in other phocid seal species studied to date. The SM/PC ratio was much higher than in other seal species or in man. In both species, the proportion of PE plasmalogens was higher in platelets than in erythrocytes. PL were more saturated in elephant seals than in fur seals. These results suggest that the erythrocytes and platelets of wild marine mammals may prove useful models to study the influence of dietary lipids on the structure and hemostatic function of these cells.

Effects of clopidogrel and its inactive form, SR 25989, on plasma, liver and platelet lipids in the rat.

The aim of the present study was to determine whether clopidogrel, one of the most potent antiplatelet compounds in vivo, could alter the lipid composition of plasma, liver tissue or platelet membranes in the rat. Animals treated (10 mg/kg per day for 7 days) with clopidogrel and its inactive analogue (R form, SR 25989) were compared with control animals. Neither compound altered plasma concentrations of triglycerides or free and esterified cholesterol, and no changes were observed in liver lipids. Clopidogrel treatment significantly lowered platelet cholesterol content and cholesterol to phospholipid ratio, while SR 25989 had comparatively smaller effects. Concerning platelet phospholipids, clopidogrel treatment reduced phosphatidylcholine(PC) but increased sphingomyelin (SP) content, whereas SR 25989 lowered PC and phosphatidylserine (PS) but raised phosphatidylethanolamine (PE) content. A significant increase in the arachidonic acid content of PE was observed only in the SR 25989 group. Clopidogrel and SR 25989 both induced an increase in the unsaturation level of platelet PC, accompanied by a decrease in the level of unsaturation in platelet SP, while a similar decrease was observed for phosphatidylinositol only in the clopidogrel group. These changes in platelet membrane composition in the clopidogrel group are probably unrelated to the antiaggregating properties of the drug, but could influence other platelet functions under long-term treatment.

Quantitative analysis of vitamin E, cholesterol and phospholipid fatty acids in a single aliquot of human platelets and cultured endothelial cells.

A reliable procedure is described for the joint analysis of vitamin E (tocopherols), cholesterol and phospholipids in the same minute sample of human platelets and on human cultured endothelial cells. The whole procedure is based on the extraction of total lipids, thin-layer chromatography of all compounds of interest and microcolumn purification of tocopherols and cholesterol. The combined use of butyl hydroxytoluene and ascorbic acid in the purification steps allowed a complete recovery of the tocopherols analyzed, as well as of cholesterol by high-performance liquid chromatography. The detection of these lipids was performed with fluorometric, spectrophotometric and evaporative light-scattering detectors whose respective sensitivities were compared. The fatty acid composition of phospholipid classes from the same sample, separated on the same silica gel plate, was determined by gas-liquid chromatography. The whole procedure is rapid since it requires about 4 h to analyse tocopherols and cholesterol and to prepare methylated fatty acids, 28 samples being easily completed within one working day. The evaluation of the whole membrane antioxidant status requires as little as one 25 cm2 confluent culture flask (about 0.75 x 10(6) cells) for endothelial cells or two ml of blood (3 x 10(8) platelets).

Food deprivation modifies fatty acid partitioning and beta-oxidation capacity in rat liver.

The involvement of lipids under starvation conditions in the shift from the phase of protein sparing (phase II) to the phase of increased protein breakdown (phase III) has been investigated. Plasma and liver were sampled from fed and unfed rats at two distinct stages which were characterized according to the changes in specific loss in daily body mass and nitrogen excretion. In the two groups of food-deprived rats corresponding to phases II and III, the liver concentration of triglycerides (micromol/g) was significantly lower, that of cholesterol significantly higher and that of the other lipid classes was moderately affected compared with concentrations in fed rats. Hepatic phospholipids had significantly higher concentrations (mol/100 mol) of 22:6(n-3) in food-deprived rats than in fed rats. Triglycerides had significantly higher concentrations of stearic and arachidonic acids in livers of both groups of food-deprived rats compared with fed rats. The total activity of carnitine palmitoyl transferase [mmol/(min x liver)] was 48% higher in rats studied at the end of phase II than in fed rats but was similar in fed rats and in rats studied at the beginning of phase III. The total activity of fatty acyl-CoA oxidase was 73% lower only in rats studied at the beginning of phase III when compared with fed rats. Our results indicate that during food deprivation the change in the rate of protein utilization is associated with important qualitative and quantitative alterations of hepatic lipids and oxidative capacity of fatty acids. These modifications appear to be related to the change from a preferential use of lipids to a preferential utilization of proteins.

Diets rich in saturated n-9 and n-3 fatty acids differentially affect the fatty acid composition of phospholipids and function of rat platelets.

The aim of the present study was to determine whether dietary intake of monounsaturated or long chain n-3 fatty acids could be effective in lowering platelet responsiveness through modulation of platelet phospholipid composition. Rats were fed diets containing 20% fat with equal cholesterol and 13a-tocopherol contents. These diets were supplemented with saturated, oleic or n-3 fatty acids, n-3 polyunsaturated fatty acids being added either pure, as eicosapentaenoic and docosahexaenoic ethyl esters, or as MaxEPA oil. Dietary n-3 fatty acids did not affect the oxidation status of plasma lipids. Oleic acid- and saturated fatty acid-rich diets led to similar enrichment of platelet phospholipids in arachidonic acid and to comparable thromboxane A(2) generation on stimulation with collagen or thrombin. Platelets of n-3-fed groups were differently enriched in eicosapentaenoic and docosahexaenoic acids at the expense of arachidonic acid. These groups displayed similar thromboxane A(2) production, although levels were lower than those for groups fed with oleic- or saturated fatty acid-rich diets. Only the MaxEPA diet led to a reduction in platelet reactivity, measurable as a small decrease in the aggregation induced by collagen. This diet was also responsible for a high cholesteroUphospholipid ratio and low a-tocopherol content in platelets. Overall results indicated that (i) only MaxEPA reduced platelet reactivity and (ii) this effect was moderate and apparently unrelated to platelet arachidonic acid content, membrane cholesterol to phospholipid ratio or thromboxane A(2) production.