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PubMed2005

Effect of diets containing linoleic acid- or oleic acid-rich oils on ruminal fermentation and nutrient digestibility, and performance and fatty acid composition of adipose and muscle tissues of finishing cattle.

Two trials were conducted to determine the effect of linoleic acid- or oleic acid-rich safflower oil on ruminal fermentation, nutrient digestion, feedlot performance, carcass characteristics, and fatty acid composition of adipose and muscle tissues of beef cattle. In both trials, cattle were fed a finishing diet based on barley grain, wheat silage, and alfalfa hay. Oils were fed at 5% of dietary DM. In a metabolism trial, four ruminally and duodenally cannulated Angus crossbred steers were subjected to linoleic acid-rich oil or oleic acid-rich oil in a crossover design with covariate periods (no oil supplementation). In a finishing trial, 16 individually fed Angus crossbred steers and heifers (eight per diet) received linoleic acid- or oleic acid-rich oils during the last 86 d of a 116-d feeding period. Ruminal pH, ammonia concentration, protozoal counts, major VFA concentrations, acetate-to-propionate ratio, polysaccharide-degrading activities, microbial N flow to the duodenum, and the efficiency of microbial N synthesis in the rumen were not affected (P = 0.18 to 0.96) by type of oil. Type of oil had no effect on total-tract apparent digestion of nutrients (P = 0.46 to 0.98). Ruminal true nutrient digestibilities did not differ between oils (P = 0.15 to 0.99), except that the linoleic acid-rich oil decreased (P = 0.05) NDF digestibility. Dry matter intake, ADG, G:F, and carcass characteristics did not differ (P = 0.11 to 0.84) between the two oils. Overall, the difference in dietary fatty acids provided to the cattle produced few changes in tissue fatty acids. Weight percentages of c9t11 CLA were unaltered by the addition of linoleic acid to the diet compared with oleic acid, probably as a result of low vaccenic acid production in the rumen, as the pathway of biohydrogenation was apparently primarily through the t10 pathway.

Adipose Tissue↗
PubMed1982

Effect of oleic acid injury on lung-heart interaction during ventricular filling.

Part of ventricular filling pressure is expended in deforming the lungs and oleic acid lung injury, which reduces lung compliance, might be expected to change the magnitude of this effect. Left ventricular pressure-volume curves from 13 treated and 13 uninjured dogs were compared. Curves were obtained by inflating a balloon in the flaccid left ventricle of the freshly dead dog. The extracardiac compliance component was determined by subtracting ventricular pressures observed when lungs were collapsed from those observed during inflation to levels duplicating both airway pressure and lung volume of uninjured dogs. We found that the respiratory system compliance opposing ventricular filling is much less than is predicted from the compliance opposing tidal ventilation. This suggests that cardiac filling imposes a local shape change rather than a general lung volume change. Injury only slightly decreased cardiac filling compliance although it markedly reduced lung inflating compliance. These results are consistent with citations showing that edema increases lung compliance by altering surface properties and airway closure with little change in tissue deformability. Thus, while edema may alter cardiac performance by changing pleural pressure, it has little influence on the pulmonary component of diastolic compliance.

Animals↗
PubMed1992

Blunted hypoxic vasoconstriction in oleic acid lung injury: effect of cyclooxygenase inhibitors.

Cyclooxygenase inhibitors have been reported to accentuate pulmonary hypertension and to improve gas exchange in oleic acid (OA) lung injury (Leeman et al. J. Appl. Physiol. 65: 662-668, 1988), suggesting inhibition of hypoxic pulmonary vasoconstriction by a vasodilating prostaglandin. To test this hypothesis, the hypoxic pulmonary vasoreactivity was examined at constant flow (Q; with an arteriovenous femoral bypass or a balloon catheter placed in the inferior vena cava) before and after OA in three groups of anesthetized and ventilated [inspired O2 fraction (FIO2) 0.4] dogs. Intrapulmonary shunt was measured using a SF6 infusion. A time control group (n = 7) had two consecutive hypoxic challenges after OA and received no drug. A treatment group (n = 6) received indomethacin (2 mg/kg iv) before the second hypoxic challenge after OA. A pretreatment group received indomethacin (2 mg/kg iv, n = 7) or aspirin (30 mg/kg iv, n = 6) before OA. In control and treated dogs, the hypoxic pulmonary vasopressor response was attenuated after OA. It was restored after indomethacin but also during the second hypoxic stimulus in the control dogs. After OA, gas exchange at FIO2 0.4 improved with indomethacin but not in controls. In pretreated dogs the hypoxic vasopressor response to hypoxia was preserved after OA, and gas exchange at FIO2 0.4 was less deteriorated compared with nonpretreated dogs (arterial O2 pressure 139 +/- 7 vs. 76 +/- 6 Torr, P less than 0.01, and intrapulmonary shunt 14 +/- 2 vs. 41 +/- 5%, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Serum radioactivity of 14C-triolein and 3H-oleic acid ingested in a test meal:a rapid test of pancreatic exocrine insufficiency.

A double-tracer technique to estimate lipid digestion was investigated. 3H-labelled oleic acid and 14C-labelled triolein were ingested in a test meal. The serum radioactivity of 3H after ingestion of labelled oleic acid depends on absorption and metabolism of free fatty acids, while serum radioactivity of 14C from triolein, in addition to the former, depends on triglycerol digestion. This study shows that the ratio between 3H and 14C 2h after the test meal gives a good qualitative and quantitative estimation of lipid digestion: the 3H/14C ratio in patients with maldigestion is significantly higher than for normals (P less than 0.01), the predictive value of the 3H/14C ratio in the diagnosis of maldigestion is high, that of a positive result being 1.0 and that of a negative 0.93, and quantitatively the 3H/14C ratio shows a highly significant correlation with faecal fat (P less than 0.001). The test is very easy to perform, lasts for only 2 h, and is without discomfort to the patient or nursing and laboratory staff. It gives information like or superior to that of faecal fat measurement.

Adult↗
PubMed2001

A novel phospholipase D of Arabidopsis that is activated by oleic acid and associated with the plasma membrane.

Oleate-dependent phospholipase D (PLD; EC 3.1.4.4) has been reported in animal systems, but its molecular nature is unkown. Multiple PLDs have been characterized in plants, but none of the previously cloned PLDs exhibits the oleate-activated activity. Here, we describe the biochemical and molecular identification and characterization of an oleate-activated PLD in Arabidopsis. This PLD, designated PLDdelta, was associated tightly with the plasma membrane, and its level of expression was higher in old leaves, stems, flowers, and roots than in young leaves and siliques. A cDNA encoding the oleate-activated PLD was identified, and catalytically active PLDdelta was expressed from its cDNA in Escherichia coli. PLDdelta was activated by free oleic acid in a dose-dependent manner, with the optimal concentration being 0.5 mM. Other unsaturated fatty acids, linoleic and linolenic acids, were less effective than oleic acid, whereas the saturated fatty acids, stearic and palmitic acids, were totally ineffective. Phosphatidylinositol 4,5-bisphosphate stimulated PLDdelta to a lesser extent than oleate. Mutation at arginine (Arg)-611 led to a differential loss of the phosphatidylinositol 4,5-bisphosphate-stimulated activity of PLDdelta, indicating that separate sites mediate the oleate regulation of PLDdelta. Oleate stimulated PLDdelta's binding to phosphatidylcholine. Mutation at Arg-399 resulted in a decrease in oleate binding by PLDdelta and a loss of PLDdelta activity. However, this mutation bound similar levels of phosphatidylcholine as wild type, suggesting that Arg-399 is not required for PC binding. These results provide the molecular information on oleate-activated PLD and also suggest a mechanism for the oleate stimulation of this enzyme.

Amino Acid Sequence↗
PubMed2002

Construction of an RAPD linkage map and localization of QTLs for oleic acid level using recombinant inbreds in mustard (Brassica juncea).

RAPD markers were employed for construction of a linkage map and localization of QTLs for oleic acid level using a set of 94 recombinant inbred lines (RILs) of mustard (Brassica juncea L.) as a mapping population. Only 30% of the 235 random primers used were useful in terms of polymorphism detected and the reproducibility of those patterns. Normal Mendelian segregation was observed for the majority of the 130 markers obtained with 71 informative primers; only 13.1% deviated (P < 0.01) from the expected 1:1 ratio. One-hundred and fourteen markers were assigned to 21 linkage groups (LGs) covering a total length of 790.4 cM with an average distance of 6.93 cM between markers. Two quantitative trait loci (QTL) for oleic acid level were mapped to 14- and 10.6-cM marker intervals on two different LGs. Both loci together explained 32.2% of phenotypic variance. One major QTL explained 28.5% of the trait variance observed in this species.

Breeding↗
PubMed2002

Targeting of malate synthase 1 to the peroxisomes of Saccharomyces cerevisiae cells depends on growth on oleic acid medium.

The eukaryotic glyoxylate cycle has been previously hypothesized to occur in the peroxisomal compartment, which in the yeast Saccharomyces cerevisiae additionally represents the sole site for fatty acid beta-oxidation. The subcellular location of the key glyoxylate-cycle enzyme malate synthase 1 (Mls1p), an SKL-terminated protein, was examined in yeast cells grown on different carbon sources. Immunoelectron microscopy in combination with cell fractionation showed that Mls1p was abundant in the peroxisomes of cells grown on oleic acid, whereas in ethanol-grown cells Mls1p was primarily cytosolic. This was reinforced using a green fluorescent protein (GFP)-Mls1p reporter, which entered peroxisomes solely in cells grown under oleic acid-medium conditions. Although growth of cells devoid of Mls1p on ethanol or acetate could be fully restored using a cytosolic Mls1p devoid of SKL, this construct could only partially alleviate the requirement for native Mls1p in cells grown on oleic acid. The combined results indicated that Mls1p remained in the cytosol of cells grown on ethanol, and that targeting of Mls1p to the peroxisomes was advantageous to cells grown on oleic acid as a sole carbon source.

Cell Division↗
PubMed1986

Cardiac dysfunction during acute lung injury induced by oleic acid in dogs.

Circulatory abnormalities are common during the adult respiratory distress syndrome and contribute importantly to the high mortality seen with this illness, but what causes them is not well characterized. Oleic acid-induced acute lung injury is an experimental model of the human syndrome in which hemodynamic changes are also common. To characterize a possible link between lung injury and cardiac dysfunction in this model, we evaluated cardiac function in mongrel dogs after oleic acid administration. Stroke volume index decreased, the radionuclide ventriculographically determined ejection fraction decreased, and end-diastolic volume increased after oleic acid. These results suggested a decrease in myocardial contractility, a conclusion confirmed when other experiments demonstrated a consistent rightward displacement of the end-systolic pressure-diameter relationship after oleic acid. Histologic examination of the myocardium showed little evidence of vascular injury, and myocardial tissue wet-to-dry weight ratios were normal. Thus, although the pulmonary effects of oleic acid are due to microvascular injury, similar mechanisms are not responsible for the depression in myocardial contractility.

Acute Disease↗
PubMed1999

Regulation of plasma and liver total cholesterol levels by dietary oleic acid in rats fed a high-cholesterol diet.

The effects of diets containing fats and oils or fatty acids on the lipid metabolism were investigated in male rats of the Wistar strain fed hypercholesterolemic diets, especially focusing our attention on the correlation between dietary oleic acid (OLE) contents and the levels of plasma and liver total cholesterol (T-CHOL) or the fatty acid profiles in plasma and liver CHOL-ester. In the rats fed the free (FR)-type fatty acids, the concentrations of plasma and liver T-CHOL were high and the amounts of neutral steroids excreted into the feces were low when compared with those of rats given the triacylglycerol (TG)-type fatty acids, showing that TG-type fatty acids suppress the intestinal CHOL absorption more than the FR-type fatty acids do. The concentrations of plasma T-CHOL were highest in rats fed the oleic acid (OLE)-rich diets, followed in order by rats supplied with the palmitic acid (PAL)-rich diets, the hydrogenated coconut oil (HCO) diet, and the linoleic acid (LIN)-rich diets; the lowest was in rats given tristearin (TSTE) and linseed oil (LIS) diets. A positive correlation was obtained between the dietary OLE contents and the levels of plasma and liver T-CHOL or OLE in the plasma and liver CHOL-ester, and an inverse correlation between dietary OLE contents and the amounts of excreted neutral steroids. These results suggest that the dietary OLE contents regulate the levels of plasma and liver T-CHOL in CHOL-loaded rats.

Animals↗
PubMed1987

Adrenoleukodystrophy: dietary oleic acid lowers hexacosanoate levels.

Adrenoleukodystrophy (ALD) is an X-linked disorder characterized by demyelination, adrenal insufficiency, and accumulation of saturated very-long-chain fatty acids (VLFA), particularly hexacosanoate (C26:0). We treated 5 patients with adrenoleukodystrophy (3 males and 2 symptomatic female carriers) for 6 months with a diet enriched in oleic acid (C18:1) and moderately restricted in C26:0. Elevated plasma and erythrocyte levels of C26:0 decreased in a time-dependent manner during treatment. Total plasma C26:0 concentration was lowered by 50 +/- 9% (p less than 0.01); it became normal in the female carriers. The total erythrocyte level of C26:0 decreased (44 +/- 5%; p less than 0.001) into the normal range in all patients. Significant decreases were noted in the saturated VLFA composition of plasma and erythrocyte sphingomyelin and erythrocyte phosphatidylcholine during dietary treatment. In general, decreases in saturated VLFA levels were accompanied by increases in monounsaturated VLFA levels, while total VLFA values did not change. This novel approach to the treatment of adrenoleukodystrophy, in which there is an exchange of monounsaturated VLFA for the more toxic saturated VLFA, may prove clinically beneficial in this disorder.

Adrenoleukodystrophy↗
PubMed2000

Relationship between airway pressure and the distribution of gas-liquid interface during partial liquid ventilation in the oleic acid lung injury model: fluorine-19 magnetic resonance imaging study.

OBJECTIVE: To elucidate the relationship between airway pressure (Paw) and the distribution of gas-liquid interface d ring partial liquid ventilation (PLV). DESIGN: Prospective, controlled study. SETTING: A research laboratory at a university medical center. SUBJECTS: Ten Japanese white rabbits. INTERVENTIONS: Ten rabbits were tracheostomized and mechanically ventilated (F(IO2) = 1.0, tidal volume = 40 mL, respiratory rate = 25 breaths/min) under general anesthesia. In the oleic acid lung injury group (n = 5), oleic acid (0.10-0.12 mL/kg) was intravenously administered to make a lung injury model. When PaO2 became <100 torr (13.3 kPa), 15 mL/kg of perflubron was instilled into the endotracheal tube, and PLV was performed for 60 mins. In the control group, PLV was performed for 60 mins without any insult to the lung. After animals were killed under deep anesthesia, Paw was set at 0, 5, 10, 15, 20, 25, 30 cm H2O and fluorine-19 magnetic resonance imaging was performed. Pressure-volume relationship was investigated using proton magnetic resonance imaging. MEASUREMENTS AND MAIN RESULTS: Gas-liquid interface reduces fluorine-19 magnetic resonance signal. The total lung fluorine-19 signal intensity was reduced by the Paw above the lower inflection point on the pressure-volume curve, and severe lung injury interfered with establishing gas-liquid interface, especially in the dependent region, even during PLV. CONCLUSION: Paw above the lower inflection point on the pressure-volume curve established gas-liquid interface dose dependently during PLV, and severe lung injury with low compliance could cause difficulty in the establishment of gas-perflubron interface, especially in the dependent lung region.

Animals↗
PubMed2006

Reverse hexagonal phase nanodispersion of monoolein and oleic acid for topical delivery of peptides: in vitro and in vivo skin penetration of cyclosporin A.

PURPOSE: To obtain and characterize reverse hexagonal phase nanodispersions of monoolein and oleic acid, and to evaluate the ability of such system to improve the skin penetration of a model peptide (cyclosporin A, CysA) without causing skin irritation. METHODS: The nanodispersion was prepared by mixing monoolein, oleic acid, poloxamer, and water. CysA was added to the lipid mixture to obtain a final concentration of 0.6% (w/w). The nanodispersion was characterized; the skin penetration of CysA was assessed in vitro (using porcine ear skin mounted in a Franz diffusion cell) and in vivo (using hairless mice). RESULTS: The obtainment of the hexagonal phase nanodispersion was demonstrated by polarized light microscopy, cryo-TEM and small angle X-ray diffraction. Particle diameter was 181.77 +/- 1.08 nm. At 0.6%, CysA did not change the liquid crystalline structure of the particles. The nanodispersion promoted the skin penetration of CysA both in vitro and in vivo. In vitro, the maximal concentrations (after 12 h) of CysA obtained in the stratum corneum (SC) and in the epidermis without stratum corneum (E) + dermis (D) were approximately 2 fold higher when CysA was incorporated in the nanodispersion than when it was incorporated in the control formulation (olive oil). In vivo, 1.5- and 2.8-times higher concentrations were achieved in the SC and [E+D], respectively, when the nanodispersion was employed. No histopathological alterations were observed in the skin of animals treated with the nanodispersion. CONCLUSION: These results demonstrate that the hexagonal phase nanodispersion is effective in improving the topical delivery of peptides without causing skin irritation.

Administration, Topical↗
PubMed2000

Antibacterial activity of linoleic and oleic acids isolated from Helichrysum pedunculatum: a plant used during circumcision rites.

The antibacterial activity-guided fractionation of the dichloromethane extract of leaves of Helichrysum pedunculatum resulted in the isolation of linoleic and oleic acids. Linoleic acid inhibited the growth of all the Gram-positive bacterial species tested with the minimum inhibitory concentration (MIC) varying between 0.01 and 1.0 mg/ml. Oleic acid was active against three of the five Gram-positive bacteria at a MIC of 1.0 mg/ml. Both compounds were inactive against the Gram-negative species tested. A synergistic effect between the two fatty acids was observed against Staphylococcus aureus and Micrococcus kristinae.

Anti-Bacterial Agents↗
PubMed1990

Effects of PEEP on pulmonary hemodynamics in intact dogs with oleic acid pulmonary edema.

The effects of positive end-expiratory pressure (PEEP) on the pulmonary circulation were studied in 14 intact anesthetized dogs with oleic acid (OA) lung injury. Transmural (tm) mean pulmonary arterial pressure (Ppa)/cardiac index (Q) plots with transmural left atrial pressure (Pla) kept constant were constructed in seven dogs, and Ppa(tm)/PEEP plots with Q and Pla(tm) kept constant were constructed in seven other dogs. Q was manipulated by using a femoral arteriovenous bypass and a balloon catheter inserted in the inferior vena cava. Pla was manipulated using a balloon catheter placed by thoracotomy in the left atrium. Ppa(tm)/Q plots were essentially linear. Before OA, the linearly extrapolated pressure intercept of the Ppa(tm)/Q relationship approximated Pla(tm). OA (0.09 ml/kg into the right atrium) produced a parallel shift of the Ppa(tm)/Q relationship to higher pressures; i.e., the extrapolated pressure intercept increased while the slope was not modified. After OA, 4 Torr PEEP (5.4 cmH2O) had no effect on the Ppa(tm)/Q relationship and 10 Torr PEEP (13.6 cmH2O) produced a slight, not significant, upward shift of this relationship. Changing PEEP from 0 to 12 Torr (16.3 cmH2O) at constant Q before OA led to an almost linear increase of Ppa(tm) from 14 +/- 1 to 19 +/- 1 mmHg. After OA, Ppa(tm) increased at 0 Torr PEEP but changing PEEP from 0 to 12 Torr did not significantly affect Ppa(tm), which increased from 19 +/- 1 to 20 +/- 1 mmHg. These data suggest that moderate levels of PEEP minimally aggravate the pulmonary hypertension secondary to OA lung injury.

Animals↗
PubMed1987

Changes in oleic acid oxidation and incorporation into lipids of differentiating L6 myoblasts cultured in normal or fatty acid-supplemented growth medium.

L6 myoblasts accumulate large stores of neutral lipid (predominantly triacylglycerol) when cultured in fatty acid-supplemented growth medium. No accumulation of neutral lipid was evident in myotubes (differentiated myoblasts) when treated similarly. Triacylglycerol accumulation was rapid and dependent on exogenous fatty acid concentration. Triacylglycerol content in myoblasts cultured in fatty acid-supplemented growth medium was approx. 3-fold higher than that in myotubes treated similarly and 2-3-fold higher than that in myoblasts cultured in normal growth medium. Incorporation studies using [I-14C]oleic acid showed that myoblasts and myotubes take up exogenous fatty acid at similar rates. However, cells cultured in fatty acid-supplemented growth medium remove more exogenous fatty acid than do cells cultured in normal growth medium. Over 90% of the incorporated label was found in phospholipid and triacylglycerol fractions in all situations studied. Myoblasts incorporated a more significant proportion (P less than 0.001) of label into triacylglycerol compared with that of myotubes. No differences in fatty acid oxidation rates were detected when differentiating L6 cells cultured in normal growth medium were compared with those cultured in fatty acid-supplemented growth medium. However, fatty acid oxidation rates were observed to increase 3-5-fold upon myoblast differentiation. We conclude that there is a marked change in the pattern of lipid metabolism when myoblasts (primarily triacylglycerol-synthesizing cells) differentiate into myotubes (primarily phospholipid-synthesizing cells). Understanding these changes, which coincide with normal muscle development, may be important, since a defect in this natural switch could explain the observed accumulation of lipid in muscle characteristic of some of the muscular dystrophies and other lipid-storage myopathies.

Animals↗
PubMed2004

Oleic acid lung injury: a morphometric analysis using computed tomography.

BACKGROUND: The oleic acid-induced lung injury (OAI) model is considered to represent the early phase of acute respiratory distress syndrome (ARDS). Its inherent properties are important for the design and the interpretation of interventional studies. The aim of this study was to describe the evolution of morphometric lung changes during OAI using computed tomography (CT) analysis. Furthermore, the effect of a temporary change in positive end-expiratory pressure (PEEP) was evaluated. METHODS: Fifteen anaesthetized pigs were ventilated in volume-controlled mode with a baseline PEEP of 5 cm H(2)O. Helical CT scans were taken at baseline and 1 h after oleic acid injection. The PEEP was then either increased to 10 cm H(2)O (n = 5), decreased to 0 cm H(2)O (n = 5) or kept constant (n = 5) for 30 min. For the next 30 min, the baseline PEEP level was applied in all animals before the final CT scans 2 h after the induction of OAI. Dimensional and volumetric changes were determined from radiographical attenuation values. RESULTS: There was a major decrease in gas volume and an increase in tissue volume within the first hour. A net increase in total lung volume, with a larger transverse area but no displacement of the diaphragm, was manifest after 2 h. A minor increase in volume of non-aerated lung, located to the caudal region, was observed during the second hour. The tidal volume was redistributed to the middle and apical regions. The temporary change in PEEP did not influence the morphological progress of OAI. CONCLUSION: Decreased gas volume and increased tissue volume are the dominating morphometric characteristics of oleic acid lung injury, occurring mainly within the first hour. With these changes manifest, the course of injury is not affected by a limited period of moderately changed PEEP during the second hour. The net increase of total lung volume suggests a predominance of oedema formation over airway and alveolar collapse.

Animals↗
PubMed1983

In vitro response of Staphylococcus aureus from cystic fibrosis patients to combinations of linoleic and oleic acids added to nutrient medium.

The effect of supplementing nutrient substrate with various combinations of concentrations of oleic and linoleic acids on the growth of 11 strains of Staphylococcus aureus was assessed. Whereas increasing the concentration of linoleic acid by itself greatly diminished the growth of all 11 strains, concomitant increases in oleic acid greatly diminished the inhibitory effect of linoleic acid. With oleic acid in the nutrient substrate, most of the strains were induced to produce slime which surrounded the cells. Since the slime incorporated oleic but not linoleic acid, such slime production isolated the cells from direct contact with the growth inhibitor, linoleic acid.

Adolescent↗
PubMed1990

Inhibition of Na,K-ATPase and sodium pump by protein kinase C regulators sphingosine, lysophosphatidylcholine, and oleic acid.

The effects and modes of action of certain lipid second messengers and protein kinase C regulators, such as sphingosine, lysophosphatidylcholine (lyso-PC), and oleic acid, on Na,K-ATPase and sodium pump were examined. Inhibition of purified rat brain synaptosome Na,K-ATPase by these lipid metabolites, unlike that by ouabain, was subject to membrane dilution (i.e. inhibition being counteracted by increasing amounts of membrane lipids). Kinetic analysis, using the purified enzyme, indicated that sphingosine and lyso-PC were likely to interact, directly or indirectly, with Na+-binding sites of Na,K-ATPase located at the intracellular face of plasma membranes, a conclusion also supported by studies on Na,K-ATPase and 22Na uptake using the inside-out vesicles of human erythrocyte membranes. The studies also showed that ouabain (but not sphingosine and lyso-PC) increased the affinity constant (K0.5) for K+, whereas sphingosine and lyso-PC (but not ouabain) increased K0.5 for Na+. Sphingosine and lyso-PC inhibited 86Rb uptake by intact human leukemia HL-60 cells at potencies comparable to those for inhibitions of purified Na,K-ATPase and protein kinase C. It is suggested that Na,K-ATPase (sodium pump) might represent an additional target system, besides protein kinase C, for sphingosine and possibly other lipid second messengers.

Animals↗