Influence of dietary linoleic acid on leucocyte sodium transport and blood pressure

Relationship of dietary linoleic acid to blood pressure. The International Study of Macro-Micronutrients and Blood Pressure Study [corrected]

Findings from observational and interventional studies on the relationship of dietary linoleic acid, the main dietary polyunsaturated fatty acid, with blood pressure have been inconsistent. The International Study of Macro-Micronutrients and Blood Pressure is an international cross-sectional epidemiological study of 4680 men and women ages 40 to 59 years from 17 population samples in China, Japan, United Kingdom, and United States. We report associations of linoleic acid intake of individuals with their blood pressure. Nutrient intake data were based on 4 in-depth multipass 24-hour dietary recalls per person and 2 timed 24-hour urine collections per person. Systolic and diastolic blood pressures were measured 8 times at 4 visits. With several models to control for possible confounders (dietary or other), linear regression analyses showed a nonsignificant inverse relationship of linoleic acid intake (percent kilocalories) to systolic and diastolic blood pressure for all of the participants. When analyzed for 2238 "nonintervened" individuals (not on a special diet, not consuming nutritional supplements, no diagnosed cardiovascular disease or diabetes, and not taking medication for high blood pressure, cardiovascular disease, or diabetes), the relationship was stronger. With adjustment for 14 variables, estimated systolic/diastolic blood pressure differences with 2-SD higher linoleic acid intake (3.77% kcal) were -1.42/-0.91 mm Hg (P<0.05 for both) for nonintervened participants. For total polyunsaturated fatty acid intake, blood pressure differences were -1.42/-0.98 mm Hg (P<0.05 for both) with 2 SD higher intake (4.04% kcal). Dietary linoleic acid intake may contribute to prevention and control of adverse blood pressure levels in general populations.

Salt Loading Increases Urinary Excretion of Linoleic Acid Diols and Triols in Healthy Human Subjects

Increased dietary linoleic acid has been associated with reduced blood pressure in clinical and animal studies possibly mediated by prostaglandins. Urinary linoleate and prostaglandin metabolite excretion were investigated in subjects exposed to a salt-loading/salt-depletion regimen. Twelve healthy subjects were recruited from the New Orleans population (before Hurricaine Katrina) and admitted to the Tulane-Louisiana State University-Charity Hospital General Clinical Research Center after a 5-day outpatient lead-in phase on a 160-mmol sodium diet. On inpatient day 1, the subjects were maintained on the 160-mmol sodium diet, and a 24-hour urine specimen was collected. On day 2, the subjects received 2 L of IV normal saline over 4 hours and continued on a 160-mmol Na + diet (total: 460 mmol of sodium). Two 12-hour urine collections were obtained. On day 3, the subjects received three 40-mg oral doses of furosemide, two 12-hour urine collections were obtained, and the subjects were given a 10-mmol sodium diet. Urinary oxidized lipids were measured by high-performance liquid chromatography-tandem quadrupole mass spectroscopy. The excretion of the urinary linoleate metabolites, dihydroxyoctadecamonoenoic acids, and trihydroxyoctadecamonoenoic acids increased significantly during intravenous salt loading as compared with day 1 and the salt-depleted periods. The urinary excretion of 6-keto- prostaglandin F1α was unaffected by salt loading but was dramatically increased 7- to 10-fold by salt depletion. Prostaglandin E2 excretion was positively correlated with sodium excretion. The salt-stimulated production of linoleic acid diols and triols may inhibit tubular sodium reabsorption, thereby assisting in the excretion of the sodium load.

Composition of dietary fat affects blood pressure and insulin responses to dietary obesity in the dog

Cardiovascular and metabolic parameters were evaluated in 15 female spayed dogs before and after they became obese on either a saturated fat (LD, lard, n=8) or unsaturated fat (CO, corn oil, n=7) diet. Body weight and body fat increased significantly in both groups, although no differences occurred between diet groups. Dogs receiving the LD diet exhibited a greater increase in mean arterial pressure than those receiving the CO diet (p<0.01; 15.9 +/- 2.1 vs. 9.8 +/- 3.3 mm Hg increase). The CO diet stimulated a greater increase in heart rate than the LD diet (p<0.05; 32.8 +/- 7.8 vs. 14.1 +/- 5.8 bpm increase). Ganglionic blockade with chlorisondamine caused an increase in HR in both lean groups and in the obese CO group, but not the obese LD group, consistent with a decrease in parasympathetic tone to the heart in the dogs overfed saturated fat. Obesity enhanced the heart rate response to beta-adrenergic stimulation by isoproterenol in the LD, but not CO group. The LD diet increased circulating insulin and decreased insulin sensitivity, whereas the CO diet had no effect on either parameter. These findings suggest that the composition of dietary fat can modulate the autonomic and metabolic adaptations induced by dietary obesity.

Biochemical and morphological correlations in human gallbladder with reference to membrane permeability

There is good evidence that gallbladder epithelium is permeable to a diverse range of molecules which move into the epithelial cell from the lumen or the basement membrane. Morphological investigations have shown both secretory mucous droplets, components of the endocytosis pathway together with evidence of a system allowing passage of molecules across the basement membrane. This indicates that the gallbladder epithelium may be influenced by molecules presented via the apical and basal membranes, complicating our understanding of gallbladder function, particularly in disease. Gallbladder disease increases the proteoglycan content of the basement membrane, but the implication of this in terms of permeability remains to be defined. Indeed, it remains unknown whether this precedes disease or is a manifestation of the disease process. The removal of water from hepatic bile by gallbladder involves two counter ion transport systems. Autoradiography shows that ion transport occurs into the lateral intracellular spaces but it remains unclear whether this leads to a hypertonic solution in these spaces causing an osmotically driven water absorption or if the process involves an osmotically linked isotonic secretion. These ion pumps are reversible, for water is absorbed during the interdigestive phase but fluid is secreted into the lumen during digestion or in the presence of disease. Appropriate neural stimulation can increase or decrease fluid absorption from the lumen while vasoactive intestinal peptide or secretin promote fluid secretion, probably mediated by prostaglandins leading to raised cyclic AMP acting at the cellular level. Immediate control may depend on intracellular Ca2+ which activates a calmodulin-protein kinase, phosphorylating the counter ion transporters to downregulate their activity. Failure of this regulatory process may explain the initial increase in bile concentrating potential seen in the development of gallstones although the mechanism of such failure remains unknown. More concentrated bile increases movement of biliary compounds into gallbladder epithelial cells which alter gallbladder function in a complex manner. Secondary bile acids are raised in gallstone disease and increase permeability of the gallbladder epithelium to molecules including cholesterol. This cholesterol absorbed from the lumen may have paramount importance to gallbladder function. Raised biliary cholesterol reduces gallbladder motility, possibly by increasing the amount of cholesterol in gallbladder muscle membranes and reducing contraction in response to cholecystokinin. However, increased secondary bile acids are also associated with an alteration in phospholipid acyl groups which may alter ion transport activity and/or cholesterol solubility within the micelle/vesicle. As the acyl groups show increased arachidonate levels the production of prostaglandins could be raised, although currently it is not known if this phospholipid arachidonate enters the epithelial cells. In addition, gallbladder inflammation is associated with raised phospholipase A2 activity, leading to formation of fatty acids and lysophospholipid which causes membrane damage. The fatty acids are likely to displace cholesterol from the micelle but may also act directly on the epithelium, possibly increasing prostaglandin production and thus stimulating mucin secretion. Increased mucin secretion is seen early in gallstone disease but the evidence presently available cannot determine if this is a causative factor.

Hypertensive effect of polyunsaturated dietary fat

Male Sprague-Dawley rats were fed a diet high in either saturated fat (lard) or polyunsaturated fat (corn oil) beginning at 10 weeks of age. After 10 weeks of diet treatment, blood pressure (BP) was 17% higher in rats fed saturated fat and 8% higher in rats fed polyunsaturated fat than in rats fed a low-fat control diet. Rats fed the lard diet became obese, and their fasting insulin levels were elevated (38% above control). These data demonstrate that both saturated and polyunsaturated dietary fats induce hypertension.

Dietary fats, fish, and blood pressure

In humans any effects of dietary saturated fats or omega-6 polyunsaturates on blood pressure appear to be mediated by changes in caloric intake and long-term weight changes. In contrast, omega-3 fatty acids have a mild antihypertensive effect which is seen most clearly in untreated subjects with higher blood pressures, in older people, and during sodium restriction. The mechanism may be due to a combination of effects consequent to incorporation of omega-3 fatty acids into vascular phospholipids, leading to reduced formation of endothelial contractile substances in larger vessels and impairment of sympathetic neuroeffector and other vasoconstrictor mechanisms in resistance vessels.

Effects induced by olive oil-rich diet on erythrocytes membrane lipids and sodium-potassium transports in postmenopausal hypertensive women

Since we have observed that monounsaturated fatty acids (MUFA) enriched diet modifies red cell membrane lipids and cation transport systems in normotensive subjects, we similarly evaluated a group of hypertensive patients undergoing an analogous dietary modification. In a group of 18 moderately hypertensive women, the diet was supplemented for two months with olive oil (about 45 g/day), which replaced an equal amount of seasoning fats. Before and after this period, red cell fatty acid composition was evaluated by gas-chromatography in order to verify diet compliance: a significant increase in oleic acid was observed, while the content of saturated and polyunsaturated fatty acids remained unchanged. After olive oil, maximal rates of Na-K pump (5580 +/- 329 vs 6995 +/- 390, p less than 0.001) and Na-K cotransport (Na-COT 544 +/- 52 vs 877 +/- 46, p less than 0.001: K-COT 790 +/- 76 vs 1176 +/- 66, p less than 0.001), cell Na content (9.58 +/- 0.4 vs 10.61 +/- 0.6, p less than 0.03) and passive permeability for Na (936 +/- 74 vs 1836 +/- 102, p less than 0.001) rose significantly. Although the reduction in maximal rate of the Li-Na CT after olive oil was not significant, it was the only cation transport parameter being correlated with the variations of membrane lipids, namely negatively with UFA (r = -0.528, p less than 0.05) and positively with SFA (r = 0.482, p less than 0.005). The change in maximal rate of Li-Na CT was also correlated with the variation of systolic and diastolic BP (r = 0.50, p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term effects of linoleic-acid-enriched diet on albuminuria and lipid levels in type 1 (insulin-dependent) diabetic patients with elevated urinary albumin excretion

We conducted a 2-year prospective randomised study to investigate the effects of a linoleic-acid-enriched diet on albuminuria and lipid levels in Type 1 (insulin-dependent) diabetic patients with elevated urinary albumin excretion (overnight urinary albumin excretion rate between 10 and 200 micrograms/min). Thirty-eight patients were randomly assigned to increase dietary polyunsaturated:saturated fatty acids ratio to 1.0 by replacement of saturated fat with linoleic-acid-rich products (n = 18, two dropouts, analysis was performed in n = 16) or to continue their usual diet (n = 20). The total fat and protein content of the diet was unaltered. Clinical characteristics, albuminuria, blood pressure, glomerular filtration rate, metabolic control and dietary composition were similar in the two groups at baseline. In the high linoleic acid diet group, linoleic intake rose from 7 +/- 4 to 11 +/- 2 energy % and polyunsaturated:saturated fatty acids ratio rose from 0.60 +/- 0.28 to 0.96 +/- 0.16 (p less than 0.001 compared to usual diet group). The median increase albuminuria was 58% (95% confidence interval, 13 to 109) during the first year (p less than 0.02) and 55% (95% confidence interval, 11 to 127) (p less than 0.01) during the second year. Glomerular filtration rate remained unaltered and filtration fraction tended to rise (p less than 0.05 compared to usual diet group). In the usual diet group, albuminuria did not significantly increased by 16% (95% confidence interval, -17 to 38) and glomerular filtration rate declined during the second year. Blood pressure tended to rise similarly in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Salt loads raise plasma fatty acids and lower insulin

Some fatty acids are potent inhibitors of angiotensin binding and aldosterone production in adrenal glomerulosa cells and thereby may be involved in regulating salt and water balance. To study the possible regulation of fatty acids by salt, we measured the levels of unesterified fatty acids in plasma from patients subjected to extremes of dietary salt intake and saline infusion. Insulin and catecholamines, two known regulators of plasma fatty acids, also were measured. Infusion of 2 l saline over 4 hours caused the levels of most unesterified fatty acids to rise. Total unesterified fatty acids rose 60-100%. A high salt diet caused a smaller rise in total unesterified fatty acids (approximately 33%). In both instances, oleic and palmitoleic acids showed the greatest proportionate increases, whereas stearic acid was relatively unaffected. When salt loads were administered by either intravenous or dietary routes, plasma insulin levels fell by approximately 50%. Plasma norepinephrine increased after saline infusion but not during a high salt diet. Postsaline levels of fatty acids correlated inversely with postsaline levels of aldosterone, supporting a possible role for fatty acids as physiological regulators of the adrenal glomerulosa. A rise in plasma fatty acids and fall in insulin in response to salt loads could act in concert to increase sodium excretion, constituting a physiological mechanism contributing to salt and water balance.

The relationship between thromboxane and cytosolic calcium modifiers in rat platelets

Platelet activity is controlled, in part, by cytosolic free ionized calcium concentration ([Ca++]i). Regulation of platelet thromboxane (TXB2) synthesis may be by regulation of [Ca++]i. Dietary linoleate is a regulator of TXB2 synthesis, therefore, it may act by influencing [Ca++]i. Aspirin is a regulator of TXB2 synthesis by inhibition of cyclooxygenase; ouabain and nifedipine are regulators of [Ca++]i. This study was conducted to determine whether these affectors of TXB2 synthesis and [Ca++]i cause associated responses. Male nonobese Zucker rats were fed diets supplying 30% of energy (en%) as fat. Dietary fat was a mixture of corn oil and beef tallow to provide 3.0, 4.5, 6.0, or 7.5 en% linoleic acid, with cholesterol added to provide equal cholesterol in all diets. Rats were fed for 30 days with 6 rats/diet. Isolated rat platelets were assayed for FA composition; the percentage of linoleic acid in platelet FA rose linearly with increasing dietary linoleate (r = 0.76, P less than 0.0001). Resting and thrombin-stimulated platelet [Ca++]i and TXB2 synthesis were measured in the presence or absence of extracellular calcium and aspirin, ouabain, or nifedipine. Aspirin caused reductions in both parameters; nifedipine blocked [Ca++]i, but did not affect TXB2; ouabain increased both. Changes induced by those modifiers of TXB2 and platelet [Ca++]i caused changes that were in the same direction for both. CaCl2 caused an increase in both and the [Ca++]i was correlated with the square root of the TXB2; without CaCl2 the two were negatively correlated; aspirin, ouabain, and nifedipine treatments resulted in no significant correlations. The results suggest that there is a common modifier of [Ca++]i and TXB2 synthesis.

Many membrane abnormalities in hypertension result from one primary defect

Evidence has been presented that: 1.) Changes in lipid bilayer alter the function of integral membrane proteins. 2.) There is less calcium bound to the plasma membrane in hypertension. 3.) Structural and functional abnormalities of the lipid bilayer have been reported in genetic hypertension. We hypothesize that multiple abnormalities of membrane transport systems in hypertension are secondary to an inherent abnormality of the lipid bilayer in which these transport proteins reside.

A controlled trial of a low sodium, low fat, high fibre diet in treated hypertensive patients: the efficacy of multiple dietary intervention

An 8-week combination low sodium, low fat, high fibre diet was compared to the individual components of this diet in a controlled trial using 193 patients already on treatment for essential hypertension. No significant changes were observed in the high fibre group. The low sodium group showed a decrease in systolic blood pressure which was close to significance. The low fat group showed a small but significant decrease in seated diastolic blood pressure and weight. The combination group showed larger and highly significant decreases in seated and standing systolic blood pressures, seated diastolic blood pressure and weight, as well as a significant reduction in standing diastolic blood pressure. We conclude that multiple dietary intervention in this case in the form of a low sodium, low fat, high fibre diet, is more effective than any single dietary intervention and is useful in patients already on medication.

Effect of a monounsaturated diet vs. a polyunsaturated fatty acid-enriched diet on blood pressure in normotensive women and men

The effect on blood pressure of monounsaturated and (n-6)polyunsaturated fatty acids was studied under strict dietary control in normotensive subjects. For 17 days 31 women and 27 men received a control diet providing 19.3% of energy as saturated fat. Then subjects were randomized over two test diets: one diet provided 15.1% of energy from monounsaturated and 7.9% from polyunsaturated fatty acids ('mono diet'), and the other diet provided 10.8% from monounsaturated and 12.7% from polyunsaturated fatty acids ('poly diet'). Saturated fat intake was now 12.8% on both diets. Mean blood pressure at the end of the control period was 116/69 mmHg for the mono group and 117/73 mmHg for the poly group. After 5 weeks on the test diet, blood pressure was 115/67 mmHg for the mono group and 117/72 mmHg for the poly group (difference in changes between the two diet groups was not significant). These findings suggest that at a high fat intake, linoleic acid, when providing more than 7.9% of energy intake, does not influence blood pressure relative to oleic acid in normotensive women and men.

Dietary linoleic acid prevents the development of deoxycorticosterone acetate-salt hypertension

The aim of this study was to elucidate the effect of dietary variations of linoleic acid on the development of deoxycorticosterone acetate (DOCA)-salt hypertension in rats. All rats were divided into three groups and fed one of the following isocaloric diets with 8% NaCl: a high linoleic acid (HLA) (20% sunflower oil), a moderate linoleic acid (5% lard oil + 15% sunflower oil), or a low linoleic acid (DLA) (20% lard oil). After 4 weeks of feeding, we determined intraerythrocyte sodium, potassium, and magnesium concentrations, intra-aortic and lymphocyte magnesium content, and erythrocyte ouabain-sensitive 22Na efflux rate constant. Cytoplasmic free calcium concentration of lymphocytes from thymus was also determined with quin-2 as a fluorescent indicator. In the HLA group, the elevation of systolic blood pressure was significantly attenuated, and intraerythrocyte sodium concentration was significantly lower than in the DLA group. There were greater intraerythrocyte potassium and magnesium concentrations, intra-aortic and lymphocyte magnesium contents, and erythrocyte ouabain-sensitive 22Na efflux rate constant in the HLA group as compared with other groups. Cytoplasmic free calcium concentration in the HLA group was significantly lower than in other groups. Systolic blood pressure significantly correlated negatively with intraerythrocyte and intra-aortic magnesium concentrations and intraerythrocyte potassium concentration, and correlated positively with cytoplasmic free calcium concentration. Erythrocyte ouabain-sensitive 22Na efflux rate constant significantly correlated positively with intraerythrocyte magnesium concentration. These findings suggest that dietary linoleic acid can attenuate the development of DOCA-salt hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmembrane cation fluxes and fatty acid composition of erythrocytes in psoriatic patients

Cation transport systems and lipid composition of erythrocyte membrane were studied in 27 psoriatic patients and in 34 healthy individuals. Whereas intracellular Na and K content, Na- and K-passive permeability and Li-Na countertransport of psoriatics did not show any statistical difference from normals, the Na/K ATPase pump activity was significantly higher and Na-K cotransport was significantly lower. Membrane lipid composition of psoriatics was different from normals: an increase in arachidonic acid and in unsaturated (poly- and total unsaturated) fatty acid content was found. A positive correlation was demonstrated between unsaturated/saturated fatty acid ratio and Na/K ATPase pump activity. These results demonstrate an alteration of erythrocyte Na/K ATPase pump and Na-K cotransport in psoriasis. These alterations of cation transport are associated with a perturbation of membrane fatty acid composition which appears a widespread phenomenon in cells of psoriatic patients.

Blood pressure in spontaneously hypertensive rats fed butterfat, corn oil, or fish oil

Dietary fats have been shown to influence blood pressure in humans and animal models of hypertension. The ability of a particular fat to modulate arterial pressure appears to depend on its fatty acid profile rather than its degree of saturation or unsaturation. Little is known about the effects of specific dietary fats of animal origin on blood pressure. We tested the concurrent effects of both calcium and dietary fat on blood pressure development in the spontaneously hypertensive rat. Sixty animals were fed diets containing butterfat, fish oil, or corn oil from 3-26 weeks of age. Each diet among the three oils was further modified to contain either 0.25% or 2.0% of the diet as calcium. All six diets provided 18% of the diet (36% of the calories) as fat. The polyunsaturated-to-saturated fat ratio was 0.07, 0.84, and 4.54 for butterfat, fish oil, and corn oil, respectively. Fish oil consumption resulted in lower blood pressures compared with butterfat (p less than 0.036) or corn oil (p less than 0.0009). Similarly, butterfat feeding resulted in lower blood pressures when compared with corn oil (p less than 0.054). Supplementing the diet with calcium decreased blood pressure in both the butterfat and corn oil diets. When butterfat diets were supplemented with calcium, the resulting blood pressures did not differ significantly from those obtained with the two fish oil diets. It is concluded that butterfat, though highly saturated, is associated with less of an increase in the spontaneously hypertensive rat's blood pressure than is corn oil, which is highly unsaturated.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane fatty acids, glutathione-peroxidase activity, and cation transport systems of erythrocytes and malondialdehyde production by platelets in Laurence Moon Barter Biedl syndrome

The fatty acid composition of erythrocyte membrane, the glutathione-peroxidase activity of erythrocytes and platelets, the production of malondialdehyde by platelets and the activity of the main systems of transmembrane cation transport have been studied in 5 members of a family, 2 of whom affected by Laurence-Moon-Barter-Biedl Syndrome. A remarkable increase of polyunsaturated fatty acids (particularly arachidonic acid) and of cholesterol/phospholipid molar ratio has been noted. This pattern of membrane lipids was associated to an increment of malondialdehyde production and an increase activity of glutathione-peroxidase. Serum retinol and a-tocopherol were in the normal range, whereas serum selenium was low in 3 out of 5 members. Moreover, the alteration of membrane lipids was associated to a decrease of the maximal velocity of Li-Na countertransport. We speculate that the enrichment of polyunsaturated fatty acids on the cell membranes may represent a condition favoring the lipoperoxidation and therefore the development of the retinitis pigmentosa characteristic feature of Laurence-Moon-Barter-Biedl Syndrome.

The antihypertensive effects of fish oil. A controlled study of polyunsaturated fatty acid supplements in essential hypertension

Both n-3 and n-6 polyunsaturated fats have been suggested to lower blood pressure, an effect ascribed to altered biosynthesis of eicosanoids. To test these hypotheses, we studied blood pressure and eicosanoid production during supplementation of dietary fat for four weeks in 32 men with mild essential hypertension. Supplementation was preceded and followed by four-week run-in and recovery periods. Groups of eight subjects received either 10 ml or 50 ml of fish oil (3 or 15 g of n-3 fatty acids) daily, 50 ml of safflower oil (39 g of n-6 fatty acids), or 50 ml of a mixture of oils that approximated the types of fat present in the American diet. The biosynthesis of eicosanoids was assessed by the measurement of urinary metabolites. Blood pressure decreased in the men who received the high dose of fish oil (systolic pressure by a mean of 6.5 mm Hg [P less than 0.03] and diastolic pressure by 4.4 mm Hg [P less than 0.015]), but not in the other groups. Although the formation of vasodilatory prostacyclins (prostaglandins I2 and I3) increased initially, this increase was not maintained as blood pressure fell. The level of thromboxane A2 metabolites fell; metabolites of thromboxane A3 were detected in the groups receiving fish oil. The formation of prostaglandin E2 increased during supplementation with safflower oil and tended to decrease with fish oil; no prostaglandin E3 metabolite was detected. Our data indicate that high doses of fish oil can reduce blood pressure in men with essential hypertension. However, the clinical usefulness and safety of fish oil in the treatment of hypertension will require further study.

The effect of Intralipid infusion on the human leucocyte sodium-pump in vivo

1. The effect of unsaturated long-chain non-esterified fatty acids (NEFA) on the human leucocyte sodium-pump was studied in vivo. 2. Plasma NEFA level was raised acutely from 0.28 (SD 0.10) to 2.54 (SD 0.48) mmol/l by infusion of 'Intralipid 20%' (trademark) at 90 ml/h with heparin, and the human leucocyte 22Na efflux rate constants were studied in eight normal weight males. 3. After 3 h, there was a significant lowering of the total (from 3.97 (SD 0.92) to 3.10 (SD 0.71)/h; P less than 0.01) and ouabain-sensitive 22Na efflux rate constants (from 2.89 (SD 0.55) to 2.37 (SD 0.62)/h; P less than 0.02). Ouabain-insensitive efflux rate constants showed a tendency to fall (from 1.08 (SD 0.51) to 0.73 (SD 0.23)/h). Leucocyte potassium content remained unchanged, but sodium content rose from 31 (SD 12) to 38 (SD 18) mmol/kg dry weight (P less than 0.05). Total, ouabain-insensitive and ouabain-sensitive efflux rates did not change significantly during the Intralipid-heparin infusion. 4. Plasma insulin levels rose gradually throughout the 3 h infusion period. 5. In conclusion, NEFA, when raised to pathological levels, can inhibit the leucocyte Na-pump in vivo even in the presence of physiological levels of serum albumin, and may increase insulin secretion.

Change in blood pressure in relation to change in nutrients effected by manipulation of dietary sodium and potassium

1. As part of a study investigating the effect of dietary alterations of sodium and potassium intake on blood pressure, the changes in nutrients that occurred with dietary intervention were determined. 2. Mild hypertensive subjects were randomized to one of four dietary intervention groups: control; high potassium; low sodium; low sodium, high potassium. The changes in nutrients in each diet group were assessed by dietary history and five repeat 24 h dietary recalls. Assessment was validated by measurement of urinary nitrogen excretion and urinary electrolytes. 3. The three dietary intervention groups experienced a fall in blood pressure (systolic: 4.4 +/- 1.0 mmHg, P less than 0.005; diastolic: 3.3 +/- 0.7 mmHg, P less than 0.001), greater than that observed in the control group. 4. The only significant dietary change across all diet groups was a reduction in the dietary sodium/potassium ratio, which was significantly less than that of the control group. The only other nutrient to differ from the control in all groups was fat intake, which was reduced. 5. In the control group there was a small but significant decrease in energy, fibre, protein, carbohydrate, potassium and magnesium intake. In the high potassium group there was a significant increase in fibre, carbohydrate, potassium, magnesium, and a decrease in calcium intake. In the low sodium group there was a decrease in energy intake with a subsequent reduction in all nutrients except alcohol. In the low sodium, high potassium group there was a significant reduction in dietary sodium and protein and an increase in fibre, carbohydrate, potassium and magnesium. 6. The reduction of the dietary sodium/potassium ratio correlated with a reduction in the urinary sodium/potassium ratio. This was the best predictor for change in diastolic pressure in all groups, suggesting that reduction in the sodium/potassium ratio contributed to the fall in blood pressure. 7. Reduction of sodium intake and increase in potassium intake by dietary means caused a reduction in blood pressure which does not appear to be due to alteration of other measured dietary constituents.