Changes produced by trematode larvae in the phospholipid fatty acid composition of digestive gland of the mollusc Littorina saxatilis

Lipids of the digestive gland of the mollusc Littorina saxatilis from the White and Barents Seas were studied. Changes of its biochemical composition are discussed in the connection with different temperature of the habitat and with infestation with trematode larvae. Comparative analysis of the fatty acid (FA) composition of each of phospholipids in intact molluscs has revealed essential differences. Phosphatidylcholine and monophosphatidylinositol (MPI) FA did not differ in the omega 3/omega 6 ratio, which is due to their tolerance to the temperature factor, whereas more unsaturated phospholipids--phosphatidylethanolamine (FEA), its plasmalogen form (pFEA), and phosphatidylserine--differed 1.5-2 times in the studied molluscs. Predominance of omega 3 acids in the Borents Sea molluscs undoubtedly is due to the lower habitat temperatures, as it provides a higher fluidity of membrane phospholipids. Infestation affected to the greatest degree the quantitative FA composition in pFEA and MPI. At infestation, out of all considered phospholipids, only in MPI there was revealed a threefold decrease of the content of eikosenoic acid C20 : 1, whereas in all other phospholipids, in the contrary, it increased. Monophosphatidylinositols also differed essentially from other phospholipids by the saturated FA amount, which changed the unsaturation index of these phospholipids. Since the functional significance of this minor phospholipid is determined by its participation in the so-called phosphatidylinositol system of the hormonal signal transduction, it seems interesting to elucidate whether an increase of this membrane phospholipid saturation at invasion affects the reflex connection between signals from receptors located in a parasite and enzymatic processes.     

Effect of habitat and motor activity of molluscs on fatty acid composition of triglycerides and phospholipids

A comparative analysis of fatty acids (FA) in neutral lipids and phospholipids of digestive gland and pedal muscle has been performed in molluscs from various ecological groups differing by belonging to sea or fresh water, trophic types or the associated motor activity. In freshwater pulmonary gastropods Lymnaea stagnalis and Lymnaea ovalis and marine prosobranchial molluscs Buccinum undatum and Littorina littorea the total content of ω3-acids in phospholipids of the studied tissues differed more than twice, predominantly due to the combined effect of temperature and salinity of the habitat. The lower viscosity of cell membranes in marine species (ω3/ω6 < 1) is determined to the greatest degree by the presence of eicosapentaenoic acid that accounts for 22–25% of the FA sum in marine species. Comparison of the molluscs by their trophic belonging has revealed the presence of linoleic acid in triglycerides in digestive glands of phytophages (8–12%), but the practically complete absence of this acid in the predator B. undulatum (< 0.8%). By mobility, L. littorea inhabiting the high-low tide littoral was inferior to freshwater pulmonary gastropods and to the marine predator, as it stops moving twice a day during the low tide. In phospholipids of pedal muscle of this mollusc the amount of long-chain polyunsaturated C: 22 FA was 3–6 times lower than that in other studied species, which might possibly indicate the role of these acids in functioning of the pedal muscle contractile tissue. On the whole, use of the FA characteristics as the parameters determining belonging to certain ecological group requires a certain caution due to a complex action of biotic and abiotic factors on the animal metabolism. The exception is the ω3/ω6 ratio in total phospholipids of fresh water and marine gastropods.     

Thermoadaptation and fatty acid composition of main phospholipids of the small-scaled redfin <Emphasis Type="Italic">Tribolodon brandti</Emphasis> under natural and experimental conditions

The fatty acid (FA) composition of the main membrane phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), was investigated in the muscle, gills, and liver of the small-scaled redfin Tribolodon brandti (Dybowskii, 1872) at different temperatures under natural and experimental conditions. It was established that a water temperature decrease in the natural habitat was accompanied by an increase in polyunsaturated fatty acid contents and the unsaturation index, mainly at the expense of FAs of the ω3 series (20:5ω3 and 22:6ω3), and by a decrease in saturated fatty acid levels in PC and PE. A similar, but less pronounced tendency was revealed in experiments with a rapid lowering of water temperature. These findings suggest the weak adaptation ability of the small-scaled redfin to a drastic shift of environmental temperature. Temperature changes produced the greatest alterations in the FA composition of phospholipids in the liver and the smallest changes occurred in muscle tissue.     

Thermal Adaptation and Fatty Acid Composition of Major Phospholipids in the Plain Sculpin <Emphasis Type="Italic">Myoxocephalus jaok</Emphasis> at Different Temperatures of Natural Habitat

The composition of phospholipids (PLs), fatty acids (FAs), molecular species of major membrane lipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE) as well as the cholesterol (CL) level in the gills and liver of the plain sculpin Myxocephalus jaok were analyzed at different habitat temperatures (18, 9, 0°C). Polar lipids and cholesterol were shown to be actively involved in adaptation of the plain sculpin to changes in environmental temperature. A decrease in temperature evoked multidirectional changes in the level of monoenoic (MUFA) and polyenoic (PUFA) FAs, ω-3 PUFA, etheric PLs, and in the unsaturation index (UI) of FAs in PC and PE of th e plain sculpin organs. Changes in the composition of PL molecular forms were unidirectional in all organs but showed some organ specificity. Thus, PC showed an increase in the total percentage of SFA/PUFA and MUFA/PUFA containing predominantly 20:5, 22:5 and 22:6 of PUFA and a decrease in the percentage of SFA/MUFA and PUFA/PUFA as well as in the level of alkylacyl forms of PC. PE showed an increase in the percentage of MUFA/PUFA and a decrease in that of SFA/PUFA and PUFA/PUFA as well as in the level of alkenylacyl forms of PE. Despite a close FA composition of PC and PE, the repertoire of their molecular forms differed in an organ- and temperature-dependent manner. Molecular mechanisms of thermal adaptation in the plain sculpin organs were traced more distinctly at the level of PC and PE molecular forms rather than in their FA spectrum.     

Comparative study of lipids and fatty acids in blood plasma of river lamprey Lampetra fluviatilis and brown frog Rana temporaria at the periods of elimination of exogenous feeding

Lipids of blood plasma of lampreys and frogs are composed of phospholipids, triglycerides, free fatty acids (FA), cholesterol, cholesterol esters, and waxes. The lipids content in plasma of frogs is markedly lower as compared with that of lampreys. However, the percentage of lipid components is represented by close values. Fluidity of triglycerides and phospholipids in lampreys is determined predominantly by monoenic acids and polyenoic acids of the ω-3-type, whereas that in frogs—by monoenic acids and polyenic acids of the ω-6-type. Free FA are represented mainly by saturated and monoenic acids.     

Effect of total hypothermia on the fatty acid composition of blood phospholipids of rats and sousliks and light irradiation on chemical processes in lipid extract

Effect of hypothermia on the fatty acid composition of rat and souslik blood phospholipids is studied. Different reaction of these animals to cooling is revealed: in rats no changes were observed in the fatty acid composition of blood phospholipids, whereas in the hibernating there were significant changes in the content of individual fatty acids (FA). The content of monoenic acids in sousliks decreased almost by 50%, while the content of saturated acid (C18) and of polyenic acids C18 : 2omega6 and C20 : 4omega6 rose significantly. Such changes seem to be the mechanism that promotes maintenance of the organism viability under conditions of a decreased level of metabolism, heart rhythm, and body temperature and is evolutionarily acquired. At the same time, the observed changes in the content of individual FA do not lead to sharp changes in such integrative parameters as the total non-saturation of phospholipids, which determines liquid properties of chylomicrons and other lipolipoprotein transport particles of the souslik blood. There are studied absorption spectra of blood lipid extracts of rats and sousliks under effect of light as well as effect of light upon the FA composition of lipid extracts of these animals. The FA composition of lipid extracts has been established to remain practically constant, whereas the character of changes of spectra under action of light indicates the presence in the extracts of oxidation-reduction reactions. The obtained data allow suggesting that in the lipid extract there occurs cooperation both of the phospholipid molecules themselves and of them with other organic molecules, which makes it possible for fatty acids to participate in processes of transport both of electrons and of protons. This novel role of FA as a participant of the electron transfer might probably be extrapolated to chemical reactions (processes) occurring inside the membrane.     

Erythrocyte insulin receptor characteristics and erythrocyte membrane lipid composition in healthy men

The cell membrane plays an important role in the mechanism of insulin action. To test whether erythrocyte insulin receptor characteristics are related to the erythrocyte membrane lipid composition, 11 healthy volunteers were studied. The relationship between insulin binding to erythrocytes, the number of receptors per cell and the affinity of receptors to insulin on the one hand and total phospholipid fatty acid (FA) composition and cholesterol/phospholipid molar ratio in the erythrocyte membrane on the other hand were evaluated. 1. We found a significant negative correlation between specific insulin binding and the proportion of n-6 essential FA in erythrocyte membrane phospholipids, especially linoleic acid (r = -0.82, p less than 0.01) and arachidonic acid (r = -0.73, p less than 0.05). On the other hand, a significant positive correlation between insulin binding and the proportion of nonessential FA (r = +0.65, p less than 0.05) was seen. Number of receptors per cell and the affinity of receptors were not significantly related to phospholipid FA composition. 2. There was no significant correlation between insulin receptor characteristics and the cholesterol/phospholipid molar ratio in the erythrocyte membrane. The data presented support the hypothesis that the FA pattern of membrane total phospholipids may modify the properties of insulin receptors.     

Content of the main lipid components in blood serum lipoproteins of human and of some animal species

Using precipitation method, low-density (LDL) and high-density (HDL₂ and HDL₃) lipoproteins were isolated from blood serum of human (donors and patients with ischemic heart diseases—IHD, bronchial asthma—BA, chronic obstructive bronchitis—(COB) and mammals predisposed (pig, rabbit) and resistant (rat, mink, Arctic fox) to atherosclerosis, of birds (hen, pigeon), of bony fish (trout, white-fish, pike-perch, pike, bream, burbot), and of cartilaginous fish (sturgeon, white sturgeon). From each lipoprotein group, lipids were extracted, separated by thin-layer chromatography, and analyzed quantitatively by spectrophotometric method. In phosphatidylcholine and HDL₂ cholesterol esters, bound fatty acids (FA) were determined by gas-liquid chromatography. The main amount of total cholesterol has been established to be present in human LDL, especially in the cases of IHD, and in LDL in mammals predisposed to atherosclerosis. In mammals resistant to atherosclerosis and in fish the almost entire cholesterol was revealed in HDL. The phospholipid (phosphatidylcholine) was represented by the ω6-series. Acids of the ω3-series accounted for a negligible percentage, especially in IHD. On the contrary, the HDL FA composition in poikilothermal animals (fish) was characterized by a very high content of polyunsaturated FA of the ω3-series. It is concluded that by the example of several studied species and of human, composition of lipid components in animal lipoproteins has a non-stable character and is submitted to changes. Their most pronounced modifications with a negative trend were revealed in human LDL and HDL in IHD.     

Modulating role of lipids and their fatty acids in adaptation of the White Sea mussels <Emphasis Type="Italic">Mytilus edulis</Emphasis> L. to environmental salinity change

Role of lipids and fatty acids (FA) in littoral and sublittoral White Sea mussels Mytilus edulis L. was studied at various stages of reproductive cycle in the phenotypic adaptation (acclimation) to changes of the sea water salinity. The obtained data indicate differences in the mussel lipid and fatty acid spectra, which are connected both with their location (littoral or sublittoral) and with the spawning period stage (3b—release of gametes or 3c—resorption of residual sex products). Lipids and FA of both mussel groups respond to the salinity changes to the greater degree at the 3b than at the 3c stage. In the littoral mussels at the 3b and 3c stages there were revealed differently directed changes in the content of membrane lipid—cholesterol—and in the cholesterol: phospholipids ratio. In the sublittoral mussels that are less adapted to extreme action of abiotic factors, more significant changes were found in the lipid and FA compositions.     

Effect of total hypothermia on the fatty acid composition of blood phospholipids of rats and ground squirrels and of the light irradiation on chemical processes in lipid extract

Effect of hypothermia on the fatty acid composition of rat and ground squirrel blood phospholipids is studied. Different reaction of these animals to cooling is revealed; in rats no changes were observed in the fatty acid composition of blood phospholipids, whereas in the winterhibernating ground squirrels there were significant changes in the content of individual fatty acids (FA). The content of monoenic acids in ground squirrels decreased almost by 50%, while the content of saturated acid (C18) and of polyenic acids C18: 2ω6 and C20: 4ω6 rose significantly. Such changes seem to be the mechanism that promotes maintenance of the organism viability under conditions of a decreased level of metabolism, heart rhythm, and body temperature and is evolutionary acquired. At the same time, the observed changes in the content of individual FA do not lead to sharp changes in such integrative parameters as the total non-saturation of phospholipids, which determines liquid properties of chylomicrons and other lipolipoprotein transport particles of the ground squirrel blood. There are studied absorption spectra of blood lipid extracts of rats and ground squirrels under effect of light as well as effect of light upon the FA composition of lipid extracts of these animals. The FA composition of lipid extracts has been established to remain practically constant, whereas the character of changes of spectra under action of light indicates the presence in the extracts of oxidation-reduction reactions. The obtained data allow suggesting that in the lipid extract there occurs cooperation of both the phospholipids molecules themselves and of them with other organic molecules, which makes it possible for fatty acids to participate in processes of transport both of electrons and of protons. This novel role of FA as a participant of the electron transfer might probably be extrapolated to chemical reactions (processes) occurring inside the membrane.     

Limit of change in unsaturation index of fatty acid composition of phospholipids at adaptation of molluscs to biogenic and abiogenic environmental factors

Comparative study of fatty acid composition of total phospholipids, as well as of phosphatidylcholine and phosphatidylethanolamine from hepatopancreas and leg muscle was carried out on several representatives of gastropod molluscs (Gastropoda) and on the bivalve mussel Mytilus edulus (Bivalvia). The objects of our study were marine littorins Littorina saxsatilis adapted to different temperature conditions of White Sea and Barents Sea, the freshwater lymnaea Lymnaea stagnalis infested by Trematoda, and mussels from the White and Black Seas. It was shown that depending on the existence conditions of the studied tissue or lipid, the maximal changes occurred in the percentage of saturated acids (4–83%); the percentage of unsaturated acids was less expressed (1–14%) and the changes in unsaturation index (UI), on average, did not exceed 20%. It was suggested that the revealed quantitative restriction of the UI change under the action of various external factors is a limit for maintenance of the membrane fluidity necessary for normal cell viability, specifically in the studied ectothermic molluscs.     

FATTY ACID CONTENT AND CHEMICAL COMPOSITION OF FRESHWATER MICROALGAE1

Fatty acid (FA), total lipid, protein, amino acid, carbon, nitrogen, and phosphorus content was analyzed in 24 samples of freshwater microalgae. The samples originated from batch, continuous, or mass cultures in various growth phases and from net samples from lakewater. FA were analyzed quantitatively by using an internal standard in a GLC system and expressed as mg·g^?1 dry weight (DW). The FA of one group of blue-greens (e.g. Oscillatoria and Microcystis) were similar to those of the greens with higher amounts of 18C acids of the ω3 type compared to the ω6 type, whereas the other group (e.g. Anabaena and Spirulina) contained mostly ω6 acids. The flagellates, a taxonomically diverse group, were characterized by high amounts of long-chained (20–22 C) polyunsaturated FA (PUFA), particularly of the ω3 type. The ω3/ω6 ratio appears to be highest in algae in the exponential growth phase. The increased lipid content in stressed algae was mostly due to increased saturated fatty acids and ω6 acids, whereas the valuable ω3 acids were unchanged or even decreased. Amino acid composition (% of total amino acids) did not vary much betaken species, but when analyzed quantitatively (mg-g^?1 DW), varied considerably between species and within species in different growth phases. The nitrogen and phosphorus contents were variable in all three algal groups. The relationship between PUFA and phosphorus content differed among the algal groups. The data suggest that PUFA in the phospholipids consist mostly ω3 acids.     

Alien molluscs affect the composition and diversity of native macroinvertebrates in a sandy flat of Lake Neuchâtel,Switzerland

The spread of alien molluscs is a serious threat to native biodiversity in fresh waters. Alien freshwater molluscs may deplete the resources of native species and alter the physical structure of the habitat through their shell mass. These changes might have both positive and negative effects on native community members. We investigated the native macroinvertebrate community in relation to the densities of four alien mollusc species (Corbicula fluminea, Dreissena polymorpha, Potamopyrgus antipodarum and Lithoglyphus naticoides) in a sandy flat of Lake Neuchatel, Switzerland. The habitat examined was dominated by these alien mollusc species. The abundance of the alien molluscs did not directly impact the native community assembly. However, C. fluminea and D. polymorpha influenced the composition and diversity of native macroinvertebrates by transforming the sandy substratum into a partly hard substratum habitat. Substantial differences in community composition between shallow (<3.5 m) and (≥5 m) deep sites were recorded. At shallow sites, the abundance of D. polymorpha was significantly reduced as a result of depth-selective feeding of ducks. A controlled shell decay study revealed that shells of alien molluscs (C. fluminea, D. polymorpha) persist for a longer period in the sediment than those of native molluscs. Consequently, shells of alien molluscs have a long-lasting impact by modifying the sandy habitat. This form of ecosystem engineering favours the occurrence of several native taxa, but is disadvantageous for other taxa with specific habitat requirements, and thus can be regarded as an indirect impact of competition.     

Bounds of change in unsaturation index of fatty acid composition of phospholipids at adaptation of molluscs to biogenic and abiogenic factors of external medium

Comparative study of fatty acid composition of total phospholipids, as well as of phosphatidylcholine and phosphatidylethanolamine from hepatopancreas and leg muscle was performed on several representatives of gasteropods (Gastropoda) molluscs and bivalve (Bivalvia) mussel (Mytilus edulus). The objects of our study were marine litorins (Littorina saxsatilis) adapted to different temperature conditions of White Sea and Barents Sea, freshwater lymnaea (Lymnaea stagnalis) infested by Trematoda and mussels from White Sea and Black Sea. It was shown that depending on the existence conditions of studied tissue or lipid, the maximal change is observed in the percentage of saturated acids (4-83 %), the percentage of unsaturated acids was less expressed (1-14 %) and the changes in unsaturation index (UI) did not exceed 20 % on average. It was supposed that observed quantitative bounds of UI change under the action of different external factors is utmost for maintenance of membrane fluidity necessary for normal vital activity of cell, particularly in studied ectothermic molluscs.     

Greater effect of diet than exercise training on the fatty acid profile of rat skeletal muscle.

We determined the interaction of diet and exercise-training intensity on membrane phospholipid fatty acid (FA) composition in skeletal muscle from 36 female Sprague-Dawley rats. Animals were randomly divided into one of two dietary conditions: high-carbohydrate (64.0% carbohydrate by energy, n = 18) or high fat (78.1% fat by energy, n = 18). Rats in each diet condition were then allocated to one of three subgroups: control, which performed no exercise training; low-intensity (8 m/min) treadmill run training; or high-intensity (28 m/min) run training. All exercise-trained rats ran 1,000 m/session, 4 days/wk for 8 wk and were killed 48 h after the last training bout. Membrane phospholipids were extracted, and FA composition was determined in the red and white vastus lateralis muscles. Diet exerted a major influence on phospholipid FA composition, with the high-fat diet being associated with a significantly (P < 0.01) elevated ratio of n-6/n-3 FA for both red (2.7-3.2 vs. 1.0-1.1) and white vastus lateralis muscle (2.5-2.9 vs. 1.2). In contrast, alterations in FA composition as a result of either exercise-training protocol were only minor in comparison. We conclude that, under the present experimental conditions, a change in the macronutrient content of the diet was a more potent modulator of skeletal muscle membrane phospholipid FA composition compared with either low- or high-intensity treadmill exercise training.     

Mitochondrial activity,hemocyte parameters and lipid composition modulation by dietary conditioning in the Pacific oyster Crassostrea gigas

Several parameters can affect membrane lipid composition in bivalves, including diet. Although two fatty acids (FA) 22:6n-3 and 20:5n-3 are essential membrane components, they are sparingly synthesized by bivalves and must be obtained from their diet. Here, effects of dietary modifications of membrane lipid composition were studied at both cellular and subcellular levels in the oyster Crassostrea gigas. To this end, we compared oysters fed two monoalgal diets that differed markedly in their FA composition and a mix of both. As expected, algae impacted phospholipids, in particular 22:6n-3 and 20:5n-3, reflecting differences of dietary microalgae FA composition. Meantime, total saturated FA, total monounsaturated FA, total polyunsaturated FA and total non-methylene-interrupted FA varied little and phospholipid class composition was only slightly affected by diets. Measures made in hemocytes indicated that only mitochondrial membrane potential was affected by diets. Total ROS production as well as mitochondrial superoxide production did not differ with diet. There was no difference in phosphorylating (state 3) and non-phosphorylating (state 4) rates of oxygen consumption rates or in cytochrome c oxidase activity of mitochondria isolated from gills between the three diets. Similarly, neither cytochromes a, b, c or c ₁ content nor citrate synthase activities were changed, suggesting that number and morphology of mitochondria were not affected by dietary treatment. These results suggest that oysters could possess high homeostatic capabilities, at both cellular and subcellular levels, to minimize the effect of dietary FA and related membrane lipid FA modifications on mitochondrial functions. These capabilities could be a means to face variations in diet composition in their natural environment and to preserve important oyster physiological functions such as growth and reproduction.     

Effect of Membrane Phospholipid Composition and Charge of the Signal Peptide of Escherichia coli Alkaline Phosphatase on Efficiency of Its Secretion

The secretion of the Escherichia coli alkaline phosphatase with a different charge of signal peptide due to replacement of positively charged Lys(–20) has been studied depending on the phospholipid composition of the membranes and the activity of the translocational ATPase—protein SecA. Changing the signal peptide charge, along with a change in phospholipid composition, has been shown to reduce the efficiency of secretion. In the absence of phosphatidylethanolamine the membrane contains anionic phospholipids only, and the dependence of secretion on the signal peptide charge decreases. The dependence of secretion on membrane phospholipid composition and the signal peptide charge is also determined by the activity of SecA protein. If SecA is inactivated by sodium azide, then the dependence of secretion on anionic phospholipids increases; on the contrary, higher content of anionic phospholipids (in the absence of phosphatidylethanolamine) decreases the dependence of secretion on the SecA activity. The results suggest a direct interaction of positively charged signal peptide with negatively charged membrane phospholipids under initiation of secretion and also interdependent contribution of the signal peptide charge, anionic phospholipids, and translocational ATPase to secretion.     

On Adaptative Changes of Rates of Oxygen Consumption and Lipid Metabolism in Littorina saxatilis at Parasitic Invasions

Effects of parasites as a biotic factor on physiological and some biochemical characteristics of gastropod molluscs Littorina saxatilis are considered. The individuals infected at young age and incapable for reproduction due to parasitic castration have a lower intensity of respiration as compared with non-infected individuals of the same size. Large infected individuals that had time to realize their reproductive potential before pathological changes in hepatopancreas do not differ in respiration from the normal individuals. Comparative analysis of the lipid fraction of liver, particularly of the fatty acid (FA) composition of total lipids and phospholipids, allowed revealing essential differences between the control and infected individuals, as well as between infected individuals of different age groups. The absence of glycogen in the liver of infected L. saxatilis, which is revealed using thin-layer chromatography, indicates functional disturbances, including those in glycogen synthesis. We suggest that the reduction of intensity of metabolism in infected individuals is connected with peculiarities of digestive process at structural changes in the hepatopancreas damaged by sporocysts. In infected molluscs the FA composition relates mainly to parasite tissues than to the liver itself. In this connection, the role of lipids in regulation of enzyme activity and permeability of cell membranes is directed first of all to maintenance of parasite metabolism. The revealed elevated synthesis of stearic acid in infected individuals can be connected with its accumulation in parasite adipose cells. The FA composition of phospholipids in infected individuals had changes that can be directed to realization of barrier function of cell membranes, specifically to restriction of the rate of oxygen diffusion into sporocysts owing to condensation of membranes. Together with adaptive changes in FA composition the ratios saturated FA : unsaturated FA and 3 : 6 acids in control and infected individuals were preserved at the constant level, which in any case is connected with maintenance of normal functioning of cell membranes.     

Dietary fatty acid composition changes mitochondrial phospholipids and oxidative capacities in rainbow trout red muscle

Dietary conditioning of juvenile trout changed the acyl chain composition of mitochondrial phospholipids and the oxidative capacities of muscle mitochondria. Trout were fed three diets differing only in fatty acid (FA) composition. The highly unsaturated 22:6 n-3 (DHA) accounted for 0.4, 14, and 30% of fatty acids in Diets 1, 2 and 3. After 10 weeks of growth, the dietary groups differed markedly in FA composition of mitochondrial phospholipids, with significant dietary effects for virtually all FA. Mean mitochondrial DHA levels were 19, 40 and 33% in trout fed Diets 1, 2 and 3. Mitochondrial oxidative capacities changed with diet, while mitochondrial concentrations of cytochromes and of the adenylate nucleotide translocase (nmol mg¹ protein) did not. Mitochondria from fish fed Diet 1 had higher non-phosphorylating (state 4) rates at 5°C than those fed other diets. When phosphorylating (state 3) rates differed between dietary groups, rates at 5 and 15°C were higher for fish fed the more unsaturated diets. Stepwise multiple regressions indicated that FA composition could explain much (42–70%) of the variability of state 4 rates, particularly at 5°C. At 15°C, FA composition explained 16–42% of the variability of states 3 and 4 rates. Similar conclusions were obtained for the complete data set (trout fed diets 1, 2 and 3) and for the data from trout achieving similar growth rates (e.g. those fed Diets 1 and 2). Neither general characteristics of membrane FA, such as % saturates, unsaturation index, n-3, n-6 or n-3/n-6 nor levels of abundant unsaturated FA such as DHA or 18:1(n-9 + n-7), were systematically correlated with mitochondrial capacities even though they differed considerably between trout fed the different diets. Relatively minor FA (20:5n-3, 20:0, 18:2n-6, 18:3n-3, 18:0 and 15:0) showed better correlations with mitochondrial oxidative capacities. This supports the concept that acyl chain composition modulates mitochondrial capacities via interactions between membrane proteins and specific FA of particular phospholipid classes in their microenvironment.     

Effect of prolactin on the phospholipid composition and cholesterol level in liver microsomes of the carp during acclimation to different temperatures

The phospholipid composition, content of cholesterol and its esters in the carp (Cyprinus carpio L.) liver microsomes depend on the environmental temperature. The free cholesterol amount and cholesterol/phospholipids ratio in microsomes decrease after the lowering of temperature from 20 to 5 degrees C. The temperature elevation to 30 degrees C results in an increase of the cholesterol ester content. The relative proportions of phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin, phosphatidyl inositol, phosphatidyl serine, phosphatidic acid increase with a significant decrease of the unidentified phospholipids amount at 30 degrees C. Prolactin affects the cholesterol content and phospholipid composition of liver microsomes. The hormone has a more pronounced effect at subextremal temperatures (5 and 30 degrees C). The actions of prolactin and temperature on the cholesterol content are similar. The hormone influence on the membrane phospholipid composition is opposite to the effect of the temperature acclimation. The possible role of prolactin in the temperature adaptation of the membrane lipids metabolism in poikilotherms is discussed.