Turnover of nonessential fatty acids in cardiolipin from the rat heart

Cardiolipin (CL) is a unique phospholipid (PL) found in the mitochondria of mammalian cells. CL remodeling is accompanied by turnover of its fatty acid acyl groups. Abnormalities in CL remodeling have been found in Barth's syndrome, diabetes, and obesity. The objective of this study was to determine nonessential fatty acid turnover in CL and phosphatidylethanolamine (PE) in the rat heart in vivo. Sprague-Dawley rats were fed either a regular chow or a high-fat diet for 15 weeks, and consumed 6% deuterium-enriched drinking water as a tracer for 14 days. CL and PE were extracted from cardiac tissue and isolated by TLC. Fatty acids from CL, PE, and plasma were analyzed by GC/MS for deuterium incorporation. Results showed oleate and vaccenate turnover were the highest in CL whereas palmitate and stearate turnover were low. Among the nonessential fatty acids in PE, turnover of stearate and vaccenate were the highest. The high turnover rate in vaccenate was unexpected, because vaccenate previously had no known metabolic or physiologic function. In conclusion, the similarly high turnover rates of both oleate and vaccenate readily suggest that remodeling is an important functional aspect of PL metabolism in CL.     

Effects of fatty acids on phosphatidylcholine biosynthesis in isolated hamster heart

The effects of stearic, oleic, and arachidonic acids on phosphatidylcholine biosynthesis in the hamster heart were investigated. When hamster hearts were perfused with labelled choline in the presence of fatty acids, biosynthesis of phosphatidylcholine was stimulated only by stearic acid. Stearic acid was found to accumulate in unesterified (free) form in the hamster heart after perfusion. The stimulation by stearic acid was mediated in vivo by an enhancement of CTP:phosphocholine cytidylyltransferase activity in the microsomal fraction of the hamster heart and the enzyme activity in the cytosolic fraction was not affected. In contrast with the observations in rat hepatocytes, cytidylyltransferase from the hamster heart was not stimulated directly by stearic acid. The selective activation of the microsomal enzyme when the heart was perfused with stearic acid suggests that activation of the enzyme was mediated via the modification of the membrane by stearic acid.     

Effects of hypoxia and reoxygenation on adult rat heart cell metabolism

Isolated adult rat heart cells were used to study the effects of oxygen deprivation followed by reoxygenation upon myocardial metabolism. Calcium-tolerant nonbeating myocytes were incubated for 5, 30, or 60 min under 100% oxygen or 100% nitrogen and then rinsed with oxygenated buffer. Substrate oxidation was studied by incubating the cells with 14C-labeled glucose, pyruvate, or octanoate and determining the rates of 14CO2 production from the individual substrates. After 5 min of hypoxia, metabolism of glucose, as assessed by glucose oxidation and lactate production, was significantly depressed. Pyruvate and octanoate oxidation were unaltered. Oxygen consumption was also unchanged by short-term hypoxia and reoxygenation. With reoxygenation after 30 min of oxygen deprivation, more exaggerated changes in glucose metabolism were noted as well as a depression in pyruvate oxidation and unaltered octanoate oxidation. Oxidation of octanoate was slightly depressed after 60 min of hypoxia. Cell viability assessed after reoxygenation was not significantly altered until 60 min of oxygen deprivation. The results indicate that cytosolic changes occur after short periods of hypoxia followed by reoxygenation, whereas mitochondrial function is more resistant to damage inflicted by hypoxia and reoxygenation.     

Cerebral amino acids and energy metabolites in the growth retarded rat fetus under normoxia and hypoxia.

The effect of intrauterine growth retardation (IUGR) on striatal energy metabolites and amino acid concentrations was studied in the fetuses of eight nulliparous rat dams after uterine artery ligation on day 18 of gestation. On day 22 (term = 23), four dams were subjected to normoxia and four to hypoxia (10% oxygen) for 58 min, while monitoring hemodynamics and blood gases. After decapitation of the dam, fetuses were delivered by sectio and decapitated. The measured parameters in the dams were stable under normoxia but exhibited decreased oxygen availability under hypoxia. Striatal energy balance was preserved in IUGRs, both under maternal normoxic and hypoxic conditions, compared to appropriately grown (AGA) littermates. Under maternal normoxia, the striatal concentration of aspartate was reduced (P < 0.01) in IUGRs and the level of alanine was increased (P < 0.01) as compared to AGAs. Under hypoxia, the level of GABA was higher in IUGRs (P < 0.01). Lactate was increased in all fetuses under hypoxia. It is concluded that striatal energy metabolism is preserved in IUGR rat fetuses in late gestation under both maternal normoxia and hypoxia. Amino acid metabolism, however, is disturbed and depends on the degree of growth retardation and on the severity of perinatal stress.     

Effects of hypoxia on contents of essential elements in pika and rat heart

The effects of hypoxia on the levels of essential macroelements and trace elements (K, Na, Ca, Mg, Cu, Zn, Fe, and Mn) in the heart muscles of Wistar rats and plateau pikas (Ochotona curzoniae) were studied by atomic absorption spectrometry. Unlike the rat, the plateau pika is tolerant to hypoxia. The levels of K, Na, and the trace element Mn were not significantly changed in rat or pika hearts after exposure to hypoxia for 1, 10, or 25 d at simulated altitudes of 5000 and 7000 m. Other minerals (Ca, Mg, Cu, Zn, and Fe) were significantly affected by hypoxia and the levels followed different time-courses under different hypoxic regimes in these two animals. There were marked differences between the rat and pika in myocardial accumulation of essential elements such as Ca, which was increased to high levels in the rat but not affected in the pika. The results suggest that hypoxia affects animal physiological mechanisms by regulating the levels of essential elements.     

Whole body distribution of deuterated linoleic and alpha-linolenic acids and their metabolites in the rat

Little is known about the uptake or metabolism of essential fatty acids (EFAs) in various mammalian organs. Thus, the distribution of deuterated alpha-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) and their metabolites was studied using a stable isotope tracer technique. Rats were orally administered a single dose of a mixture (20 mg each) of ethyl D5-18:3n-3 and D5-18:2n-6, and 25 tissues per animal were analyzed for D5-labeled PUFAs at 4, 8, 24, 96, 168, 240, 360, and 600 h after dosing. Plasma, stomach, and spleen contained the highest concentrations of labeled precursors at the earliest time points, whereas other internal organs and red blood cells reached their maximal concentrations at 8 h. The time-course data were consistent with liver metabolism of EFAs, but local metabolism in other tissues could not be ruled out. Brain, spinal cord, heart, testis, and eye accumulated docosahexaenoic acid with time, whereas skin accumulated mainly 20:4n-6. On average, approximately 16-18% of the D5-18:3n-3 and D5-18:2n-6 initial dosage was eventually accumulated in tissues, principally in adipose, skin, and muscle. Approximately 6.0% of D5-18:3n-3 and 2.6% of D5-18:2n-6 were elongated/desaturated and stored, mainly in muscle, adipose, and the carcass. The remaining 78% of both precursors was apparently catabolized or excreted.     

Subcellular distribution of energy metabolites in the pre-ischaemic and post-ischaemic perfused working rat heart

Isolated working rat hearts were subjected to 20 min of global ischaemia and either 5 min or 15 min of reperfusion. The subcellular distribution of ATP, ADP, AMP, phosphocreatine and Pi were determined before and after ischaemia by the method of non-aqueous tissue fractionation. Ventricular function and the cytosolic, mitochondrial and ATPase-associated compartmentation of metabolites were measured. After 5 min of reperfusion, only 13 +/- 9% of the pre-ischaemic contractile function was restored compared to 67 +/- 8% after 15 min reperfusion. ATP was reduced in all cellular compartments after 5 min of reperfusion but was only decreased from pre-ischaemic values in the cytosolic compartment after 15 min of reperfusion (17.1 +/- 3.9 nmol/mg vs. 4.3 +/- 1.5 nmol/mg total protein; P less than 0.05). The mitochondrial [ATP]/[ADP] was reduced from a normal value of 4.36 to 1.79 after 5 min but recovered to 4.62 after 15 min of reperfusion. Most of the Pi was located in the mitochondria or with the ATPase fraction of the cell, with only 16% of the total Pi free in the cytosol. This study indicates that the capacity of the heart to recover function may be compromised during early reperfusion by a 59% increase in mitochondrial phosphate content and during late reperfusion by a reduced cytosolic/mitochondrial concentration ratio of both ATP (from 0.85 to 0.19) and phosphocreatine (from 3.9 to 1.24).     

Positional distribution of fatty acids in the phospholipids of regenerating rat liver]

The fatty acid composition and positioning in the glycerophospholipids from regenerating rat liver were investigated at different stages of the regeneration process. In the lecithins and phosphatidylethanolamines of the regenerating liver the content of arachidonic acid is lower and that of linoleic acid is higher than in the corresponding lipid fractions of normal rat liver. These deviations are maximal at 24 hours after hepatectomy i.e. at the onset of the mitosis. At any stage of the regeneration the high specifity of the fatty acid positioning characteristical for the normal liver is retained completely. The fatty acid composition of cardiolipin is not changed during the regeneration process.     

Effects of fasting on the myocardial subcellular distribution and lipid distribution of terminal p-iodophenyl-substituted fatty acids in rats

The myocardial lipid pool distribution and subcellular distribution of radiolabeled methyl-branched fatty acids in rats was evaluated under conditions of fasting (24 h) and feeding. With the unbranched iodophenyl fatty acid, fasting resulted in increased myocardial extraction and clearance time with a decrease in the incorporation into triglycerides and greater radioactivity in the mitochondrial fraction. With the monomethyl-branched analogue, the effects of fasting on lipid and subcellular distribution were minor except for a decrease in triglyceride incorporation. Like the unbranched analogue, the dimethyl-branched iodophenyl fatty acid showed increased myocardial extraction with fasting, however, this structurally-modified fatty acid showed increased rather than decreased incorporation into triglycerides.     

Long-chain free fatty acids inhibit ischaemic preconditioning of the isolated rat heart

Molecular and Cellular Biochemistry - Previous work has shown that thiophosphate, a phosphate analogue, leads to a global shift in the distribution of cellular proteins in a variety of organisms....     

Effects of exogenous fatty acids and cholesterol on aminopeptidase activities in rat astroglia

Several studies have addressed the interaction between fatty acids and lipids with central nervous system peptides. Because aminopeptidases (AP) are involved in the regulation of neuropeptides, this work studies several AP expressed in cultured astroglia, after exogenous addition of oleic and linoleic fatty acids and cholesterol to the culture medium. Alanyl-AP, arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities were analysed in whole cells using the corresponding aminoacyl-beta-naphthylamides as substrates. Oleic acid inhibits alanyl-AP, cystyl-AP and leucyl-AP activities, whereas linoleic acid inhibits alanyl-AP, arginyl-AP and tyrosyl-AP activities. Neither oleic acid nor linoleic acid modifies pyroglutamyl-AP activity. In contrast, cholesterol increases arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities, although it does not modify alanyl-AP activity. The changes reported here suggest that oleic and linoleic fatty acids and cholesterol can modulate peptide activities via their degradation route involving aminopeptidases; each of them being differentially regulated.     

A comparison of procedures to determine free fatty acids in rat heart

The level of free fatty acids in intact tissues has been found to be low but is known to rise in proportion to the extent of autolysis. Therefore, the high levels of free fatty acid reported in the cardiac lipids of rats fed rapeseed oil were reinvestigated using two different procedures for homogenization. Quick freezing and pulverization at dry ice temperature followed by lipid extraction was found to give lower values of free fatty acids (200 microgram/g of wet heart tissue) than the more commonly used technique of employing rotating blade-type homogenizers (greater than 1700 microgram/g of wet heart tissue). The amount of diglycerides was found to be 3 times greater when the latter method was used. The high levels of free fatty acid and diglyceride suggest that extensive autolysis occurs during homogenization with a rotating blade-type homogenizer. Freezing and pulverization at dry ice temperature is therefore recommended for determining intact lipid classes in rat heart.