Comparative studies on lipid peroxidation of microsomes and mitochondria obtained from different rat tissues: effect of retinyl palmitate

The effect of retinyl palmitate on the polyunsaturated fatty-acid composition, chemiluminescence and peroxidizability index of microsomes and mitochondria obtained from rat liver, kidney, brain, lung and heart, was studied. After incubation of microsomes and mitochondria in an ascorbate Fe++ system (120 min at 37 degrees C) it was observed that the total cpm/mg protein originated from light emission: chemiluminescence was lower in liver microsomes, mitochondria and kidney microsomes in the vitamin A group than in the control group. In mitochondria obtained from control rats, the most sensitive fatty acids for peroxidation were arachidonic acid C20:4 n6 in liver and docosahexaenoic acid C22:6 n3 in kidney and brain. In microsomes obtained from control rats, the most sensitive fatty acids for peroxidation were linoleic acid C18:2 n6 and C20:4 n6 in liver and C22:6 n3 in kidney. Changes in the most polyunsaturated fatty acids were not observed in organelles obtained from lung and heart. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of fatty acids, showed significant changes in liver, kidney and brain mitochondria, while in microsomes changes were significant in liver and kidney. These changes were less pronounced in membranes derived from rats receiving vitamin A. Our results confirm and extend previous observations that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.     

Pulmonary surfactant protein A inhibits the lipid peroxidation stimulated by linoleic acid hydroperoxide of rat lung mitochondria and microsomes

Reactive oxygen species play an important role in several acute lung injuries. The lung tissue contains polyunsaturated fatty acids (PUFAs) that are substrates of lipid peroxidation that may lead to loss of the functional integrity of the cell membranes. In this study, we compare the in vitro protective effect of pulmonary surfactant protein A (SP-A), purified from porcine surfactant, against ascorbate-Fe(2+) lipid peroxidation stimulated by linoleic acid hydroperoxide (LHP) of the mitochondria and microsomes isolated from rat lung; deprived organelles of ascorbate and LHP were utilized as control. The process was measured simultaneously by chemiluminescence as well as by PUFA degradation of the total lipids isolated from these organelles. The addition of LHP to rat lung mitochondria or microsomes produces a marked increase in light emission; the highest value of activation was produced in microsomes (total chemiluminescence: 20.015+/-1.735 x 10(5) cpm). The inhibition of lipid peroxidation (decrease of chemiluminescence) was observed with the addition of increasing amounts (2.5 to 5.0 microg) of SP-A in rat lung mitochondria and 2.5 to 7.5 microg of SP-A in rat lung microsomes. The inhibitory effect reaches the highest values in the mitochondria, thus, 5.0 microg of SP-A produces a 100% inhibition in this membranes whereas 7.5 microg of SP-A produces a 51.25+/-3.48% inhibition in microsomes. The major difference in the fatty acid composition of total lipids isolated from native and peroxidized membranes was found in the arachidonic acid content; this decreased from 9.68+/-1.60% in the native group to 5.72+/-1.64% in peroxidized mitochondria and from 7.39+/-1.14% to 3.21+/-0.77% in microsomes. These changes were less pronounced in SP-A treated membranes; as an example, in the presence of 5.0 microg of SP-A, we observed a total protection of 20:4 n-6 (9.41+/-3.29%) in mitochondria, whereas 7.5 microg of SP-A produced a 65% protection in microsomes (5.95+/-0.73%). Under these experimental conditions, SP-A produces a smaller inhibitory effect in microsomes than in mitochondria. Additional studies of lipid peroxidation of rat lung mitochondria or microsomes using equal amounts of albumin and even higher compared to SPA were carried out. Our results indicate that under our experimental conditions, BSA was unable to inhibit lipid peroxidation stimulated by linoleic acid hydroperoxide of rat lung mitochondria or microsomes, thus indicating that this effect is specific to SP-A.     

Vitamin A inhibits lipoperoxidation ascorbate-Fe++ dependent of rat kidney microsomes and mitochondria

In the present study it was investigated if Vitamin A supplementation could protect rat kidney microsomes and mitochondria from in vitro lipoperoxidation. After incubation of rat kidney microsomes and mitochondria in an ascorbate-Fe⁺⁺ system, at 37°C during 60 min, it was observed that the total cpm/mg protein originated from light emission (chemiluminescence) was lower in those organelles obtained from the control group when compared with the vitamin A supplemented group. The fatty acid composition of microsomes and mitochondria from control group was profoundly modified when subjected to nonenzymatic lipoperoxidation with a considerable decrease of arachidonic acid, C20:4 (n-6) and docosapentaenoic acid, C22:5 (n–3) in mitochondria and docosahexaenoic acid C22:6 (n-3) in microsomes.As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of specific fatty acids was higher in the supplemented animals than in those used as control. These results indicate that Vitamin A may act as antioxidant protecting rat kidney microsomes and mitochondria from deleterious effect.     

Peroxidation stimulated by lipid hydroperoxides on bovine retinal pigment epithelium mitochondria: effect of cellular retinol-binding protein

This study analyzes the effect of cellular retinol-binding protein (CRBP), partially purified from retinal pigment epithelium (RPE) cytosol, on the non-enzymatic lipid peroxidation induced by fatty acid hydroperoxides of mitochondrial membranes isolated from bovine RPE. The effect of different amounts (50, 75 and 100 nmol) of linoleic acid hydroperoxide (LHP), arachidonic acid hydroperoxide (AHP) and docosahexaenoic acid hydroperoxide (DHP) on the lipid peroxidation of RPE mitochondria was studied; RPE mitochondria deprived of exogenously added hydroperoxide was utilized as control. The process was measured simultaneously by determining chemiluminescence as well as polyunsaturated fatty acid (PUFA) degradation of total lipids isolated from RPE mitochondria. The addition of hydroperoxides to RPE mitochondria produces a marked increase in light emission that was hydroperoxide concentration dependent. The highest value of activation was produced by LHP. The major difference in the fatty acid composition of total lipids isolated from native and peroxidized RPE mitochondria incubated with and without hydroperoxides was found in the docosahexaenoic acid content, this decreased 40.90+/-3.01% in the peroxidized group compared to native RPE mitochondria. The decrease was significantly high: 86.32+/-2.57% when the lipid peroxidation was stimulated by 100 nmol of LHP. Inhibition of lipid peroxidation (decrease of chemiluminescence) was observed with the addition of increasing amounts (100-600 microg) of CRBP to RPE mitochondria. The inhibitory effect reaches the highest values in the presence of LHP.     

Vitamin A supplementation inhibits chemiluminescence and lipid peroxidation in isolated rat liver microsomes and mitochondria

In the present study we investigated if administration of vitamin A could protect rat liver microsomes and mitochondria from in vitro peroxidation. Appreciable decrease of chemiluminescence and lipid peroxidation was measured in microsomal membranes from rats receiving vitamin A, with respect to control animals. In membranes derived from control animals, the fatty acid composition was profoundly modified when subjected to in vitro peroxidation mediated by ascorbate-Fe⁺⁺, with a considerable decrease of 20:4 n6 and 22:6 n3 in mitochondria and 18:2 n6 and 20:4 n6 in microsomes. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of specific fatty acids was higher in supplemented animals than in control group when both kind of membranes were analyzed. These changes were less pronounced in membranes derived from rats receiving vitamin A. These results are in agreement with previous results that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.Abbreviations BHT butylated hydroxytoluene - BSA bovine serum albumin - CL chemiluminescence - PI peroxidizability index Member of Carrera del Investigador Científico, Consejo Nacional de Investigaciones Cientificas y Técnicas de la Republica Argentina     

The effect of alpha-tocopherol on lipid peroxidation of microsomes and mitochondria from rat testis

The testis is a remarkably active metabolic organ; hence it is suitable not only for studies of lipid metabolism in the organ itself but also for the study of lipid peroxidation processes in general. The content of fatty acids in testis is high with a prevalence of polyunsaturated fatty acids (PUFA) which renders this tissue very susceptible to lipid peroxidation. Studies were carried out to evaluate the effect of alpha-tocopherol in vitro on ascorbate-Fe(++) lipid peroxidation of rat testis microsomes and mitochondria. Chemiluminescence and fatty acid composition were used as an index of the oxidative destruction of lipids. Special attention was paid to the changes produced on the highly PUFA [C20:4 n6] and [C22:5 n6]. Lipid peroxidation of testis microsomes or mitochondria induced a significant decrease of both fatty acids. Total chemiluminescence was similar in both kinds of organelles when the peroxidized without (control) and with ascorbate-Fe(++) (peroxidized) groups were compared. Arachidonic acid was protected more efficiently than docosapentaenoic acid at all alpha-tocopherol concentrations tested when rat testis microsomes or mitochondria were incubated with ascorbate-Fe(++). The maximal percentage of inhibition in both organelles was approximately 70%; corresponding to an alpha-tocopherol concentration between 1 and 0.25 mM. IC50 values from the inhibition of alpha-tocopherol on the chemiluminescence were higher in microsomes (0.144 mM) than mitochondria (0.078 mM). The protective effect observed by alpha-tocopherol in rat testis mitochondria was higher compared with microsomes, associated with the higher amount of [C20:4 n6]+[C22:5 n6] in microsomes that in mitochondria. It is proposed that the vulnerability to lipid peroxidation of rat testis microsomes and mitochondria is different because of the different proportion of PUFA in these organelles The peroxidizability index (PI) was positively correlated with the level of long chain fatty acids. The results demonstrated the protective effect of alpha-tocopherol on lipid peroxidation in microsomes and mitochondria from rat testis.     

Non-enzymatic lipid peroxidation of microsomes and mitochondria from liver, heart and brain of the bird Lonchura striata: relationship with fatty acid composition

The aim of this study was to examine the fatty acid composition and non-enzymatic lipid peroxidation (LP) of mitochondria and microsomes obtained from liver, heart and brain of Lonchura striata. The percentage of total unsaturated fatty acid was approximately 30-60% in the organelles from all tissues studied. Brain mitochondria and both organelles of liver exhibited the highest percentage of polyunsaturated fatty acid (PUFA) (30 and 18%, respectively). The arachidonic acid (AA) content was 7% in mitochondria of liver and brain and 3% in heart mitochondria. The percentage of docosahexanoic acid (DHA) was 8% in brain mitochondria and approximately 2-3% in heart and liver mitochondria. The peroxidizability index (PI) of brain mitochondria and both organelles from liver was higher than that of organelles from heart and brain microsomes. Liver organelles and brain mitochondria were affected by LP, as indicated by the increase in chemiluminescence and a decrease of AA and DHA. These changes were not observed during LP of brain microsomes and both organelles from heart. These results indicate: 1) PI positively correlates with PUFA percentage and LP; 2) The resistance to LP detected in heart organelles would contribute to the cardiac protection against oxidative damage.     

Retinal fatty acid binding protein reduce lipid peroxidation stimulated by long-chain fatty acid hydroperoxides on rod outer segments

In the present study we have investigated the effect of partially purified retinal fatty acid binding protein (FABP) against nonenzymatic lipid peroxidation stimulated by hydroperoxides derived from fatty acids on rod outer segment (ROS) membranes. Linoleic acid hydroperoxide (LHP), arachidonic acid hydroperoxide (AHP) and docosahexaenoic acid hydroperoxide (DHP) were prepared from linoleic acid, arachidonic acid and docosahexaenoic acid, respectively, by means of lipoxidase. ROS membranes were peroxidized using an ascorbate-Fe(+2) experimental system. The effect on the peroxidation of ROS containing different amounts of lipid hydroperoxides (LOOH) was studied; ROS deprived of exogenously added LOOH was utilized as control. The degradative process was measured simultaneously by determining chemiluminescence and fatty acid composition of total lipids isolated from ROS. The addition of hydroperoxides to ROS produced a marked increase in light emission. This increase was hydroperoxide concentration-dependent. The highest value of activation was produced by DHP. The decrease percentage of the more polyunsaturated fatty acids (PUFAs) (20:4 n6 and 22:6 n3) was used to evaluate the fatty acid alterations observed during the process. We have compared the fatty acid composition of total lipids isolated from native ROS and peroxidized ROS that were incubated with and without hydroperoxides. The major difference in the fatty acid composition was found in the docosahexaenoic acid content, which decreased by 45.51+/-1.07% in the peroxidized group compared to native ROS; the decrease was even higher, 81.38+/-1.11%, when the lipid peroxidation was stimulated by DHP. Retinal FABP was partially purified from retinal cytosol. Afterwards, we measured its effect on the reaction of lipid peroxidation induced by LOOH. As a result, we observed a decrease of chemiluminescence (inhibition of lipid peroxidation) when adding increasing amounts (0.2 to 0.6 mg) of retinal FABP to ROS. The inhibitory effect reaches its highest value in the presence of DHP (41.81+/-10.18%). Under these conditions, bovine serum albumin (BSA) produces a smaller inhibitory effect (20.2+/-7.06%) than FABP.     

An allometric study of fatty acids and sensitivity to lipid peroxidation of brain microsomes and mitochondria isolated from different bird species

The objective of this investigation was to examine the relationship between body size, fatty acid composition and sensitivity to lipid peroxidation of mitochondria and microsomes isolated from the brain of different size bird species: manon, quail, pigeon, duck and goose, representing a 372-fold range of body mass. Fatty acids of total lipids were determined using gas chromatography and lipid peroxidation was evaluated using a chemiluminescence assay. The allometric study of the fatty acids present in brain mitochondria and microsomes of the different bird species showed a small number of significant allometric trends. In mitochondria the percentage of monounsaturated fatty acids, was significantly lower in the larger birds (r=-0.965; P<0.008). The significant allometric increase in 18:2 n-6; linoleic acid (r=0.986; P<0.0143), polyunsaturated (r=0.993; P<0.007) and total unsaturated (r=0.966; P<0.034) in brain microsomes but not in mitochondria may indicate a preferential incorporation of this fatty acid in the brain endoplasmic reticulum of the larger bird species. The brain of all birds studied had a high content of docosahexaenoic acid. However brain mitochondria but not microsomes isolated from all the birds analyzed showed a significant decrease of arachidonic and docosahexaenoic acids during lipid peroxidation. The allometric analyses of chemiluminescence were not statistically significant. In conclusion our results show absence of correlation between the sensitivity to lipid peroxidation of brain mitochondria and microsomes with body size and maximum life span.     

Melatonin preserves arachidonic and docosapentaenoic acids during ascorbate-Fe2+ peroxidation of rat testis microsomes and mitochondria

The pineal hormone melatonin (N-acetyl, 5-methoxytryptamine) was recently accepted to act as an antioxidant under both in vivo and in vitro conditions. In this study, we examined the possible preventive effect of melatonin on ascorbate-Fe(2+) lipid peroxidation of rat testis microsomes and mitochondria. Special attention was paid to the changes produced on the highly polyunsaturated fatty acids C20:4 n6 and C22:5 n6. The lipid peroxidation of testis microsomes or mitochondria produced a significant decrease of C20:4 n6 and C22:5 n6. The light emission (chemiluminescence) used as a marker of lipid peroxidation was similar in both kinds of organelles when the control and peroxidized groups were compared. Both long chain polyunsaturated fatty acids were protected when melatonin was incorporated either in microsomes or mitochondria. The melatonin concentration required to inhibit by 100% the lipid peroxidation process was 5.0 and 1.0mM in rat testis microsomes and mitochondria, respectively. IC 50 values calculated from the inhibition curve of melatonin on the chemiluminescence rates were higher in microsomes (4.98 mM) than in mitochondria (0.67 mM). The protective effect observed by melatonin in rat testis mitochondria was higher than that observed in microsomes which could be explained if we consider that the sum of C20:4 n6+C22:5 n6 in testis microsomes is two-fold greater than present in mitochondria.     

Fatty acid profiles and lipid peroxidation of microsomes and mitochondria from liver, heart and brain of Cairina moschata

Studies were done to analyze the fatty acid composition and sensitivity to lipid peroxidation (LP) of mitochondria and microsomes from duck liver, heart and brain. The fatty acid composition of mitochondria and microsomes was tissue-dependent. In particular, arachidonic acid comprised 17.39+/-2.32, 11.75+/-3.25 and 9.70+/-0.40% of the total fatty acids in heart, liver and brain mitochondria respectively but only 13.39+/-1.31, 8.22+/-2.43 and 6.44+/-0.22% of the total fatty acids in heart, liver and brain microsomes, respectively. Docosahexahenoic acid comprised 17.02+/-0.78, 4.47+/-1.02 and 0.89+/-0.07% of the total fatty acids in brain, liver and heart mitochondria respectively but only 7.76+/-0.53, 3.27+/-0.73 and 1.97+/-0.38% of the total fatty acids in brain, liver and heart microsomes. Incubation of organelles with ascorbate-Fe(2+) at 37 degrees C caused a stimulation of LP as indicated by the increase in light emission: chemiluminescence (CL) and the decrease of arachidonic acid to: 5.17+/-1.34, 8.86+/-0.71 and 5.86+/-0.68% of the total fatty acids in heart, liver and brain mitochondria, respectively, and to 4.10+/-0.61 in liver microsomes. After LP docosahexahenoic acid decrease to 7.29+/-1.47, 1.36+/-0.18 and 0.30+/-0.11% of the total fatty acids in brain, liver and heart mitochondria. Statistically significant differences in the percent of both peroxidable fatty acids (arachidonic and docosahexaenoic acid) were not observed in heart and brain microsomes and this was coincident with absence of stimulation of LP. The results indicate a close relationship between tissue sensitivity to LP in vitro and long chain polyunsaturated fatty acid concentration. Nevertheless, any oxidative stress in vitro caused by ascorbate-Fe(2+) at 37 degrees C seems to avoid degradation of arachidonic and docosahexaenoic acids in duck liver and brain microsomes. It is possible that because of the important physiological functions of arachidonic and docosahexaenoic acids in these tissues, they are protected to maintain membrane content during oxidative stress.     

Species differences in membrane susceptibility to lipid peroxidation

The susceptibility of liver microsomes to lipid peroxidation was evaluated in seven species: rat, rabbit, trout, mouse, pig, cow, and horse. Lipid peroxidation was measured as thiobarbituric acid reactive substances formed in the presence of either FeCl₃-ADP/ascorbate or FeCl₂/H₂O₂ initiating systems. For rat, rabbit, and trout microsomes, the order of susceptibility to peroxidation was rat > rabbit >> trout. The lack of peroxidation in trout microsomes could be explained by high microsomal vitamin E levels. Membrane fatty acid levels differed between species. Docosahexaenoic acid predominated in the trout, arachidonic acid in the rat, and linoleic acid in the rabbit. The contribution of individual fatty acids to lipid peroxidation reflected the degree of unsaturation with docosahexaenoic > arachidonic >>> linoleic. For all species except trout, the predicted susceptibility to peroxidation, based on the response of individual fatty acids, agreed well with directly measured microsomal peroxidation. With the exception of the trout, vitamin E content ranged from 0.083–0.311 nmol/mg microsomal protein between species, and low levels did not influence susceptibility to peroxidation. Trout microsomes peroxidized only after vitamin E depletion by prolonged incubation. The data indicate that below a vitamin E threshold, species differences in membrane susceptibility to peroxidation can be reasonably predicted based only on content of individual peroxidizable fatty acids.     

The effect of alpha-tocopherol on the lipid peroxidation of mitochondria and microsomes obtained from rat liver and testis.

The effect of intraperitoneal administration of alpha-tocopherol (100 mg/kg wt/24 h) on ascorbate (0.4 mM) induced lipid peroxidation of mitochondria and microsomes isolated from rat liver and testis was studied. Special attention was paid to the changes produced on the highly polyunsaturated fatty acids C20:4 n6 and C22:6 n3 in liver and C20:4 n6 and C22:5 n6 in testis. The lipid peroxidation of liver mitochondria or microsomes produced a significant decrease of C20:4 n6 and C22:6 n3 in the control group, whereas changes in the fatty acid composition of the alpha-tocopherol treated group were not observed. The light emission was significantly higher in the control than in the alpha-tocopherol treated group. The lipid peroxidation of testis microsomes isolated from the alpha-tocopherol group produced a significant decrease of C20:4 n6 , C22:5 n6 and C22:6 n3, these changes were not observed in testis mitochondria. The light emission of both groups was similar. The treatment with alpha-tocopherol at the dose and times indicated showed a protector effect on the polyunsaturated fatty acids of liver mitochondria, microsomes and testis mitochondria, whereas those fatty acids situated in testis microsomes were not protected during non enzymatic ascorbate-Fe2+ lipid peroxidation. The protector effect observed by alpha-tocopherol treatment in the fatty acid composition of rat testis mitochondria but not in microsomes could be explained if we consider that the sum of C20:4 n6 + C22:5 n6 in testis microsomes is 2-fold than that present in mitochondria.     

Changes in mitochondrial and microsomal lipid peroxidation and fatty acid profiles in adrenal glands, testes, and livers from alpha-tocopherol-deficient rats

Studies were done to evaluate the effects of alpha-tocopherol deficiency in rats on the fatty acid composition and sensitivity to lipid peroxidation (LP) of mitochondria and microsomes from adrenal glands, testes, and livers. In control (alpha-tocopherol-sufficient) animals, adrenal concentrations of alpha-tocopherol were approximately 10 times greater than those in livers and testes. Dietary deficiency of alpha-tocopherol for 8 weeks decreased adrenal and hepatic concentrations by 80-90% and testicular concentrations by approximately 60-70%. Incubation of testicular or hepatic mitochondria and microsomes from control rats with FeSO(4) (1.0 mM) caused a time-dependent stimulation of LP as indicated by the formation of thiobarbituric acid reactive substances (TBARS); the rate of TBARS production increased in preparations from alpha-tocopherol-deficient animals. TBARS formation was not demonstrable in adrenal mitochondria or microsomes from alpha-tocopherol sufficient rats, but reached high levels in alpha-tocopherol-deficient preparations. The fatty acid composition of mitochondria and microsomes was tissue-dependent. In particular, arachidonic acid comprised approximately 40% of the total fatty acids in adrenal membranes, but only 20-25% in testes and livers. alpha-Tocopherol deficiency increased oleic acid concentrations in adrenal and hepatic mitochondria and microsomes but not in testes. In all three tissues, linoleic acid concentrations decreased by approximately 50%, but arachidonic acid levels were unaffected by alpha-tocopherol deficiency. The results indicate a close relationship between tissue sensitivity to LP in vitro and alpha-tocopherol concentrations. Nonetheless, any oxidative stress in vivo caused by alpha-tocopherol deficiency seems to spare arachidonic acid in mitochondria and microsomes but decreases linoleic acid concentrations. It is possible that because of the important physiological functions of arachidonic acid, metabolic adaptations serve to maintain membrane content during periods of oxidative stress.     

Non-enzymatic lipid peroxidation of microsomes and mitochondria isolated from liver and heart of pigeon and rat

Studies were carried out to determine the level of ascorbate-Fe2+ dependent lipid peroxidation of mitochondria and microsomes isolated from liver and heart of rat and pigeon. Measurements of chemiluminescence indicate that the lipid peroxidation process was more effective in mitochondria and microsomes from rat liver than in the same organelles obtained from pigeon. In both mitochondria and microsomes from liver of both species a significant decrease of arachidonic acid was observed during peroxidation. The rate C18:2 n6/C20:4 n6 was 4.5 times higher in pigeon than in rat liver. This observation can explain the differences noted when light emission and unsaturation index of both species were analysed. A significant decrease of C18:2 n6 and C20:4 n6 in pigeon liver mitochondria was observed when compared with native organelles whereas in pigeon liver microsomes only C20:4 n6 diminished. In rat liver mitochondria only arachidonic acid C20:4 n6 showed a significant decrease whereas in rat liver microsomes C20:4 n6 and C22:6 n3 decreased significantly. However changes were not observed in the fatty acid profile of mitochondria and microsomes isolated from pigeon heart. In the heart under our peroxidation conditions the fatty acid profile does not appear to be responsible for the different susceptibility to the lipid peroxidation process. The lack of a relationship between fatty acid unsaturation and sensitivity to peroxidation observed in heart suggest that other factor/s may be involved in the protection to lipid peroxidation in microsomes and mitochondria isolated from heart.     

Lipoperoxidation of rod outer segments of bovine retina is inhibited by soluble binding proteins for fatty acids

In the present study it was investigated if soluble-binding proteins for fatty acids (FABPs) present in neural retina show protection from in vitro lipoperoxidation of rod outer segment membranes (ROS). After incubation of ROS in an ascorbate-Fe⁺⁺ system, at 37°C during 90-120 min, the total cpm originated from light emission (chemiluminescence) was found to be lower in those membranes incubated in the presence of soluble binding proteins for fatty acids. The fatty acid composition of rod outer segment membranes was substantially modified when subjected to non-enzymatic lipoperoxidation with a considerable decrease of docosahexaenoic acid (22:6 n-3) and arachidonic acid (20:4 n-6). As a result of this, the unsaturation index, a parameter based on the maximal rate of oxidation of specific fatty acids was higher in the native and control membranes when compared with peroxidized ones. A similar decrease of chemiluminescence was observed with the addition of increasing concentrations of native or delipidated FABP retinal containing fractions to rod outer segment membranes. These results indicate that soluble proteins with fatty acid binding properties may act as antioxidant protecting rod outer segment membranes from deleterious effect.     

Fatty acid composition and lipid peroxidation induced by ascorbate-Fe2+ in different organs of goose (Anser anser)

Many reports have demonstrated that birds show a low degree of fatty acid unsaturation and lipid peroxidation compared with mammals of similar body size. The aim of the present study was to examine fatty acid profiles, non-enzymatic lipid peroxidation and vitamin E levels of mitochondria and microsomes obtained from liver, heart and brain of goose (Anser anser). The unsaturated fatty acid content found in mitochondria and microsomes of all tissues examined was approximately 60% with a prevalence of C18:1 n9 + C18:2 n6 = 50%. The 20:4 n6 + C22:6 n3 content was significantly higher in brain organelles (approx. 16%) compared with mitochondria and microsomes of liver and heart (approx. 4%). Whereas these organelles were not affected when subjected to lipid peroxidation, brain mitochondria were highly affected, as indicated by the increase in chemiluminescence and a considerable decrease of arachidonic and docosahexaenoic acids. These changes were not observed during lipid peroxidation of brain microsomes. Vitamin E content was higher in liver and heart than in brain mitochondria (1.77 +/- 0.06 and 1.93 +/- 0.13 vs. 0.91 +/- 0.09 nmol/mg protein). The main conclusion of this paper is that a lower degree of unsaturation of fatty acids in liver and heart mitochondria and a higher vitamin E level than in brain mitochondria protect those tissues against lipid peroxidation.     

Effects of Dietary Fish Oil on Polyunsaturated Fatty Acid Desaturation in Fetal and Postnatal Rats

The effects were determined of dietary fish oil on the polyunsaturated fatty acid desaturation in rats fed on fish oil-containing diets (FS group) and on non-fish oil diets (CN group) during the fetal to postnatal periods. Although the desaturase activity in the liver microsomes of the FS group was higher than that of the CN group before birth, this was not altered by dietary fish oil after birth. However, a lower 20:4n-6 concentration before and after birth, and lower linoleic acid desaturation index ((dihomo-γ-linolenic acid + arachidonic acid)/linoleic acid)) at 10 wk of age in the FS group than in the CN group were observed in the liver microsomal phospholipids. The Δ6-desaturase activity in the brain microsomes of the FS group was lower than that of the CN group. These findings suggest that an intake of dietary fish oil by dams and postnatal rats affected the arachidonic acid concentration due to the decreased desaturase activity in the rats’ microsomes.     

Influence of Dietary Conjugated Linoleic Acid and Fat Source on Body Fat and Apoptosis in Mice*

Objective: To determine whether altered dietary essential fatty acid (linoleic and arachidonic acid) concentrations alter sensitivity to conjugated linoleic acid (CLA)‐induced body fat loss or DNA fragmentation. Research Methods and Procedures: Mice were fed diets containing soy oil (control), coconut oil [essential fatty acid deficient (EFAD)], or fish oil (FO) for 42 days, and then diets were supplemented with a mixture of CLA isomers (0.5% of the diet) for 14 days. Body fat index, fat pad and liver weights, DNA fragmentation in adipose tissue, and fatty acid profiles of adipose tissue were determined. Results: The EFAD diet decreased (p < 0.05) linoleic and arachidonic acid in mouse adipose tissue but did not affect body fat. Dietary CLA caused a reduction (p < 0.05) in body fat. Mice fed the EFAD diet and then supplemented with CLA exhibited a greater reduction (p < 0.001) in body fat (20.21% vs. 6.94% in EFAD and EFAD + CLA‐fed mice, respectively) compared with mice fed soy oil. Dietary FO decreased linoleic acid and increased arachidonic acid in mouse adipose tissue. Mice fed FO or CLA were leaner (p < 0.05) than control mice. FO + CLA‐fed mice did not differ in body fat compared with FO‐fed mice. Adipose tissue apoptosis was increased (p < 0.001) in CLA‐supplemented mice and was not affected by fat source. Discussion: Reductions in linoleic acid concentration made mice more sensitive to CLA‐induced body fat loss only when arachidonic acid concentrations were also reduced. Dietary essential fatty acids did not affect CLA‐induced DNA fragmentation.     

Interaction of rat liver microsomes containing saturated or unsaturated fatty acids with fatty acid binding protein: Peroxidation effect

In the studies described here rat liver microsomes containing labeled palmitic, stearic, oleic or linoleic acids were incubated with fatty acid binding protein (FABP) and the rate of removal of¹⁴C-labeled fatty acids from the membrane by the soluble protein was measured using a model system. More unsaturated than saturated fatty acids were removed from native liver microsomes incubated with similar amounts of FABP. Thein vitro peroxidation of microsomal membranes mediated by ascorbate-Fe⁺⁺, modified its fatty acid composition with a considerable decrease of the peroxidizability index. These changes in the microsomes facilitated the removal of oleic and linoeic acids by FABP, but the removal of palmitic and stearic acids was not modified. This effect is proposed to result from a perturbation of membrane structure following peroxidation with release of free fatty acids from susceptible domains.Abbreviations BSA bovine serum albumin - FABP fatty acid binding protein