Fish oil administration as a supplement to a corn oil containing diet affects arterial prostacyclin production more than platelet thromboxane formation in the rat

The administration to male rats of 5 en % fish oil (FO) as supplement to a diet containing 5 en % corn oil (CO), selectively and markedly decreased arterial parameters (6-keto-PGF1 alpha formation and platelet antiaggregatory activity) assessed in isolated aortic segments perfused with autologous platelet rich plasma (PRP). Platelet parameters (ADP-induced aggregation, TxB2 formation in thrombin-stimulated PRP and sensitivity to exogenous PGI2) were instead minimally affected. Eicosapentaenoic acid (EPA, 20:5 n-3) did not accumulate in plasma, platelet and aorta lipids and arachidonic acid (AA, 20:4 n-6) levels declined markedly only in the plasma compartment. When FO was given alone at the same 5 en % level, both arterial and platelet parameters were similarly affected. EPA accumulated in plasma cholesterol esters and was present in appreciable concentrations also in platelets and aortic walls. AA levels declined markedly in plasma lipids and appreciably also in platelet and aorta lipids. It is concluded that a) arterial and platelet parameters are differentially affected by FO administration depending upon the presence of n-6 polyunsaturated fatty acids in the diet, b) 6-keto-PGF1 alpha production by arterial tissue does not seem to be related to changes of PG precursor fatty acid levels in the phospholipid fraction.

Non-A, non-B hepatitis: positive and negative considerations on 138 cases

In 138 patients with NANB H no correlations were observed regarding types of exposure (PTH: 19.5%, DA: 18.1%, Sporadic cases: 62.4%), age groups and periods of incubation. Precipitin lines were detected assaying by ID and/or CEP onset and recovery sera with heterologous reference sera positive for Ab or Ag, respectively, or with autologous sera; "Ag"' was present during acute phase of illness, "Ab" appeared with decrease of aminotransferases, and in most cases seroconversion was observed in accord with clinical course. In few patients double precipitin lines were evidenced (heterogeneity of Ag?), while one patient reacted with all reference sera and many others with two/three sera (two NANB viruses or two Ag/Ab systems?). Tendency towards chronicity emerged in four cases, and in these Ag/Ab systems had a different behaviour.

Increased platelet aggregability is associated with increased prostacyclin production by vessel walls in hypercholesterolemic rabbits

The influences of experimental hypercholesterolemia in the rabbit on platelet-vessel wall interactions have been studied by evaluating the aggregatory response of platelet rich plasma (PRP) to arachidonic acid (AA) stimulation and levels of 6-keto-PGF1 alpha in PRP from normal (N) and hypercholesterolemic (HC) animals prior and after perfusion through the corresponding aortas. In addition, the responses of N PRP to aggregation after perfusion through HC aortas and those of HC PRP perfused through N aortas, and the platelet response to the inhibitory effect of exogenous prostacyclin have been evaluated. The data indicate that in HC rabbits, on one side platelets are hyperreactive to AA and less sensitive to the inhibitory activity of prostacyclin and, on the other, the antiaggregatory activity and prostacyclin production of vessel walls is higher, suggesting compensatory mechanisms in the haemostatic balance.

Platelet-vessel wall interactions: effects of platelets and plasma on the antiaggregatory activity and 6 keto-PGF1 alpha production in isolated perfused aortas

An experimental model for the study of platelet-vessel wall interactions has been developed, based on perfusion of rat platelet rich plasma (PRP) through isolated rat aortas. In the perfused PRP, platelet aggregation was inhibited and levels of 6 Keto PGF1 alpha and cAMP were elevated over the values found in non perfused PRP. When PPP or buffer were perfused through the isolated artery, elevations of 6 Keto PGF1 alpha levels in the perfusate were smaller (in perfused PPP) or of shorter duration (in both perfused PPP and buffer). The presence of platelets in the perfusion fluid thus enhanced the formation of Prostacyclin by the arterial wall. Levels of 6 Keto PGF1 alpha in PRP obtained from aspirin-treated animals and in PRP from normal animals, both perfused through normal aortas, were the same, and also levels of the above metabolite in normal PRP perfused through aortas of aspirin-treated animals did not differ from those found in non perfused PRP. It is concluded, from these data, that PRP does not stimulate PGI2 formation in perfused aortas by providing cyclic endoperoxides. The experimental model developed allows the study of interactions between normal platelets and aortas from experimentally treated animals or viceversa.

In vitro effects of synthetic antioxidants and vitamin E on arachidonic acid metabolism and thromboxane formation in human platelets and on platelet aggregation

The "in vitro" effects of alpha-tocopherol, butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA) were studied on aggregation of human platelets induced by collagen and arachidonic acid (AA), on the metabolic conversion of 14C AA through the cyclooxygenase and lipoxygenase pathways and on the formation of thromboxane B2 (TXB2) in washed platelets after stimulation with collagen. Vitamin E completely inhibited AA induced platelet aggregation only at high concentration (mM) and after 10 minutes of preincubation, with limited effects on AA metabolism in platelets and no effect on TXB2 formation from endogenous substrate. BHA completely inhibited platelet aggregation in the 10(-6) M range, gave 50% inhibition of AA metabolism in the 10(-5) M range and almost complete inhibition of thromboxane formation in the 10(-4) M range. BHT was about 100 times less active on platelet aggregation and AA metabolism. The lipoxygenase and cyclooxygenase pathways were differentially affected at low concentrations of BHA and only at concentrations greater than 5 X 10(-5) M were both pathways depressed.

Differential effects of dietary fatty acids on the accumulation of arachidonic acid and its metabolic conversion through the cyclooxygenase and lipoxygenase in platelets and vascular tissue

Semisynthetic diets containing either corn oil (CO) or butter (B) (11 and 2.2 en % as linoleic acid, respectively) were fed to male rabbits for periods of 3 weeks and 3 months. The CO diet, in respect to the B diet, induced higher levels of linoleic acid (LA) and lower levels of arachidonic acid (AA) in platelet phospholipids, lower levels of AA in aortic phosphatidylinositol (PI) and accumulation of both LA and AA in liver lipids. The thresholds for aggregation with AA, but not with collagen, were higher in the CO group and the formation of thromboxane B2 (TXB2) from [14C] AA, but not from endogenous substrate after collagen stimulation, was lower in the same group. Formation of PGE2-like material by incubated aortas was higher in the B group. In the CO group, platelet cyclooxygenase appeared to be selectively depressed. The correlations among diet-induced fatty acid changes in platelet and aortic lipids, platelet aggregation and thromboxane and prostacyclin formation are discussed.

Essential fatty acid status in premature newborns fed by nasoduodenal technique

The fatty acid composition of plasma phospholipids and the triene (20:3, n=9) to tetraene (20:4, n=6) ratio in the same lipid fraction have been determined, as indices of the essential fatty acid status, in a group of 22 healthy premature newborns fed by the nasoduodenal technique. Determinations have been carried out on the first and fifth day of life for all 22 newborns, and also on the tenth and 30th day of life for 12 of them. The normal plasma levels of essential fatty acids obtained indicate a satisfactory utilization of dietary essential fatty acids under these unusual nutritional conditions.

Differential effects of probenecid on the levels of endogenous PGF2 alpha and TXB2 in brain cortex

Probenecid in single or repeated doses does not modify levels of PGF2 alpha and TXB2 in rat brain cortex. After administration of subconvulsant dose of pentamethylene tetrazole (PMT) PGF2 alpha increases sharply and rapidly declines subsequently, whereas the elevation of TXB2 is smaller but of longer duration. After probenecid pretreatment PGF2 alpha levels do not decline up to 30 minutes after the initial peak and are still elevated after 60 minutes. Levels of TXB2 tend to be reduced after pretreatment. Differences in transport process or in biosynthetic compartments for these arachidonic acid (AA) metabolites may account for the observed data.

PGF2 alpha, thromboxane B2 and HETE levels in gerbil brain cortex after ligation of common carotid arteries and decapitation

The effects of ligation of both common carotid arteries in the gerbil on the levels of PGF2 alpha, TXB2, HETE and of energy metabolites in brain cortex, have been investigated. Also, in the same experimental conditions the changes of cyclic AMP in brain cortex, cerebellum, striatum and hippocampus have been monitored. ATP, glycogen, glucose and phosphocreatine decrease whereas, lactate and cyclic AMP are enhanced in the ischemic brain, as previously reported. In contrast, levels of arachidonic acid metabolites are not modified. During ischemia following decapitation, instead, PGF2 alpha, and TXB2, show considerable increase.

Effects of Dietary Fatty Acids on Platelet Aggregation and Platelet Thromboxane B2 Production in the Rabbit

Semisynthetic isocaloric diets containing 25% of either butter or corn oil were fed to male rabbits for periods of 21 days and 2½ months. Platelet aggregation induced by threshold concentrations of collagen and sodium arachidonate and the conversion of labelled arachidonic acid were then studied. Response of platelets from butter-fed animals was considerably higher to arachidonate, whereas the thresholds for collagen-induced aggregation were similar in both groups of animals. Conversion of labelled arachidonic acid to thromboxane B2, studied at different substrate concentrations in washed platelets, was significantly higher, at low substrate concentration, at 21 days in the butter fed group, and the difference was still present after 2½ months of treatment. Conversion of arachidonic acid to the hydroxy fatty acids by lipoxygenase activity was not affected by the dietary treatments. In conclusion, the metabolic conversion of exogenous arachidonic acid to thromboxane B2 appears to be selectively affected by the type of dietary fatty acids and this effect is associated with changes in the response of platelets to aggregating concentrations of arachidonic acid.

Influence of short term dietary supplementation of different lipids on aggregation and arachidonic acid metabolism in rabbit platelets

Semisynthetic diets containing 8% by weight of either corn oil or butter were fed to male New Zealand rabbits for three weeks. The plasma cholesterol values were determined, the threshold concentrations for aggregation of platelet rich plasmas were measured for collagen and Na arachidonate, and the conversion of 14C arachidonic acid to thromboxane B2 and hydroxy fatty acids (HETE and HHT) at 10, 20 and 40 microM substrate concentrations were studied. The thresholds for arachidonate induced aggregation were lower and the amplitudes of collagen induced aggregations were greater in the butter fed than in the corn oil fed rabbits. Conversions of arachidonic acid to thromboxane B2 but not to hydroxy fatty acids were greater in the butter fed rabbits at 10 and 20 microM substrate. The observed changes were accompanied by only slight modifications of plasma cholesterol levels.

Pilot epidemiological studies in thrombosis

Some differences in the blood of farmers in Nurmijarvi, Finland, Canino, Italy, and Beltsville, Maryland in the United States apparently were associated with differences, among the areas, in the farmers' diets. Those associations suggested that diets that are high in saturated fats (Nurmijarvi) could predispose humans to develop intravascular disease. Such predisposition has been observed in experimental animals. Low levels of the parameters that are considered active in such predisposition apparently were associated with diets that were low in saturated fats (Canino) or with diets that were low in saturated and high in unsaturated fats (Beltsville). Within the limits of the experimental design, the data from the three population groups indicated that a more comprehensive study might establish a relation between diet and intravascular disease in humans.

Effects of rapeseed oil on fatty acid oxidation and lipid levels in rat heart and liver

The comparative rates of oxidation of erucic and oleic acids and of their CoA esters were studied in heart and liver mitochondria of rats fed a standard diet or semisynthetic diets containing 25% of the calories as either rapeseed oil (46.6% erucic and 10.4% eicosenoic acid) or olive oil, for a period of 5 months. The long exposure to the diet containing 25% rapeseed oil did not alter the oxidative activity of mitochondria and did not induce morphological changes in the heart. It is confirmed that erucic acid is oxidized in mitochondria at lower rates than other long chain fatty acids and that its activation as CoA derivative may be one of the rate limiting steps of the overall oxidationprocess. Total lipids and triglycerides do not significantly change in the heart whereas they increase in the liver of rats fed the diet containing rapeseed oil.

Correlation between release of free arachidonic acid and prostaglandin formation in brain cortex and cerebellum

Levels of free arachidonic acid and of prostaglandin F2alpha and E2 have been measured in both brain cortex and cerebellum of rats killed by focussed microwave irradiation, and after decapitation followed by ischemia. The same parameters were studied during incubation assays. It was found that: a) after ischemia levels of both free arachidonic acid and of prostaglandins in cerebellum are lower than in brain cortex, b) formation of prostaglandins from endogenous precursor in incubated cortex is higher than in cerebellum, c) release of free arachidonic acid occurs mainly during the time interval between the sacrifice of the animals and the beginning of the incubation, whereas prostaglandins are formed mainly during the incubation assay. The correlation between release of free arachidonic acid and prostaglandin formation is discussed.

Brain free fatty levels in rats sacrificed by decapitation versus focused microwave irradiation

Values are presented for whole brain free fatty acid levels of rats sacrificed by decapitation vs focused microwave irradiation. Free fatty acids were quantitated by specific colorimetric analysis. Within ca. 1 min of sacrifice by either decapitation or microwave, rat whole brain free fatty acid concentrations ranged from ca. 80-100 mug/g fresh tissue. If the brain remained in the head for a total of 5 min after decapitation, free fatty acid levels increased by over 100%. The free fatty acids at this time were enriched with arachidonic acid. The increase in free fatty acid levels following decapitation was completely absent in rats sacrificed by the microwave irradiation. This microwave technique could be a valuable tool in determining free fatty acid and other heat stable compounds in brain tissue.

High dose frusemide in established acute renal failure

The results of treatment with frusemide in 105 patients with established acute renal failure admitted during the past six years were reviewed and compared with control groups. Daily doses of 2,000 mg of frusemide administered from the day of admission onwards produced a significant increase in the number of patients who attained a diuresis and decreased the duration of oliguria.The reduction in the time spent in hospital and in the number of dialyses required suggests that the use of frusemide in these large doses is indicated in patients with severe established acute renal failure.