[Na+, K+, Cl-]-cotransport function and dysfunction in different forms of primary hypertension.

We investigated the effect of an increase in cell Na+ content on outward and inward unidirectional fluxes catalyzed by the [Na+, K+, Cl-]-cotransport system in human erythrocytes (incubated in Li-Rb media). Erythrocytes with low Na+ content exhibited an uncoupled K+ efflux. The increase in cell Na+ content resulted in a more marked stimulation of outward Na+, K+ than of inward Li+, Rb+ cotransport fluxes (with stoichiometries not very different from one-to-one). These results suggest that in human erythrocytes and in nonepithelial cells with small but outwardly directed electrochemical Cl- gradients, the [Na+, K+, Cl-]-cotransport system may behave as a "second pump" by using the extra energy supplied by an additional net [K+, Cl-] efflux. The [Na+, K+, Cl-]-cotransport system (of vascular cells and/or noradrenergic endings) may play two different roles in primary hypertension: (a) "defective second pump" in some essential hypertensive patients with decreased cotransport affinity for internal Na+ and (b) "compensatory second pump" in other forms of primary hypertension where abnormalities in the Na+, K+ pump or in other ion transport systems may predispose the cell to a defective extrusion of excess cell Na+ content.

Erythrocyte passive potassium flux is increased in patients with ischemic coronary disease (ICD) and in subjects with family history of ICD.

BACKGROUND: It has been proposed that ischemic coronary disease (ICD) associated potassium loss could be due to modifications of potassium permeability. We investigated whether a positive family history of ICD can influence this parameter. We have compared potassium permeability in erythrocytes from ICD patients and from positive family history subjects (FICD) with control subjects. METHODS: All patients and subjects were carefully selected for the absence of hypertension and dysmetabolic pathologies. ICD group: 24 patients (19 males, 5 females; ages 43 to 69) all affected by ischemic coronary disease, under no drug treatment; FICD group: 18 subjects (all males, ages 27 to 42) with a verified positive ICD family history, without hypertensive family history and cardiovascular pathology; control group: 16 subjects (11 males, 5 females; ages 28 to 48) without positive family history of ICD. Passive potassium efflux (PPE) was spectrophotometrically measured in K-free medium containing ouabain and bumetanide. The kinetic constant was calculated by dividing PPE by the erythrocyte potassium concentration. RESULTS: No statistically significant differences were noted between the intracellular potassium content of the three groups. However, (1) the passive potassium permeability of the ICD group was significantly higher (kK=0.055 +/- 0.021 h(-1), n=24) than that of the control group (kK=0.023 +/- 0.008 h(-1), n= 16; p<0.00001), (2) the FICD group was higher (kK=0.036 +/- 0.012 h(-1), n=18) than the control group (p<0.001), and (3) the ICD group was higher than the FICD group (p<0.001). CONCLUSIONS: Our results suggest an inheritability of ICD, paralleling the familial aggregation of the pathology. Erythrocyte potassium permeability could represent an early marker of ischemic coronary disease and be used as a prophylactic tool.

[Transmembrane sodium transport systems in various forms of hyperlipoproteinemia]. / Sistemi di trasporto transmembrana del Na+ in forme diverse di iperlipoproteinemia.

The possible interrelationships between the erythrocytic transport systems of Na+ (Na+/K+ pump, Na+/K+ cotransport, Na+/Li+ countertransport, Na+ passive permeability) and the plasmatic lipids (cholesterol, triglycerides, HDL, LDL, apoprotein A1, apoprotein B) were studied in 42 normotensive subjects with different forms of hyperlipoproteinaemia and with a negative familiarity for arterial hypertension. In subjects with hypercholesterolaemia (hyperlipoproteinaemia II A and II B) an elevated activity of the Na+/K+ pump was noticed, while in subjects with hypertriglyceridaemia (type IV) an increase in Na+ passive permeability and Na+/Li+ countertransport with a lower level of intraerythrocytic Na+ was shown. A negative correlation was observed between the total efflux of Na+ and Na+/K+ pump and the levels of cholesterol (r = -0.43, p < 0.04 and r = -0.41, p < 0.05) and the apoprotein B/A ratio (r = 0.42, p < 0.05 and r = -0.50, p < 0.01). A negative correlation was also noticed between the Na+/K+ pump and the levels of apoprotein B (r = -0.41, p < 0.05). The Na+/K+ cotransport appeared inversely correlated with the levels of HDL cholesterol (r = -0.42, p < 0.05), while the Na+ passive permeability was negatively correlated with the levels of LDL (r = -0.43, p < 0.04) and positively correlated with the plasmatic triglycerides (r = +0.54, p < 0.01). Such data show that the plasmatic lipids can influence the systems of transmembrane ionic transport of Na+ and play an important role also this way, in cardiovascular pathology.

[Effects of adrenergic stimulation on transmembrane transport of Na+ in patients with essential hypertension]. / Effetti della stimolazione adrenergica sui sistemi di trasporto transmembrana del Na+ in pazienti con ipertensione essenziale.

BACKGROUND: It has been studied whether an adrenergic stimulation induced by the cold pressor test (CPT) could influence the behaviour of the transmembrane transport systems of sodium in hypertensive subjects compared to a normotensive control population. MATERIALS AND METHODS: Twenty-two hypertensive subjects (average age 43.2 +/- 5.7 years), with normal weight, without signs of cardiovascular and metabolic diseases, underwent the cold pressor test. The dynamic behaviour of sodium erythrocytic transport systems and plasmatic norepinephrine was evaluated basally, at the third minute during the cold pressor test and 20 minutes after the end of the test. The same test was carried out in a control population made up of 20 normotensive subjects (average age 41.9 +/- 4.8 years), selected on the basis of the absence of any cardiovascular or metabolic pathology and without family history of arterial hypertension. RESULTS: The cold pressor test did not cause significant changes in the sodium transmembrane transport systems in normotensive subjects, while in the hypertensive subjects a significant reduction was observed, during the test, in the total efflux of sodium and in the sodium/potassium pump, respectively from 2636 +/- 296 mumol/l/red blood cells/hr to 2032 +/- 178 mumol/l/red blood cells/hr (p < 0.0001) and from 2156 +/- 149 mumol/l/red blood cells/hr to 1610 +/- 101 mumol/l/red blood cells/hr (p < 0.0001); the intraerythrocytic sodium increased from 6.5 +/- 1.0 mmol/l/cells to 7.2 +/- 1.1 mmol/l/cells (p < 0.04) and the passive permeability decreased from 0.039 +/- 0.004 hr-1 to 0.018 +/- 0.006 hr-1 (p < 0.0001). During cold pressor test the increase in the plasma norepinephrine levels was correlated to the reduction in the total efflux of sodium (r = -0.60; p < 0.003) and in the sodium/potassium pump (r = -0.59; p < 0.003) only in hypertensive subjects. CONCLUSIONS: Our data show that an adrenergic stimulation, induced by the cold pressor test, is able to significantly influence the behaviour of transmembrane fluxes of sodium in hypertensive subjects, and it causes an inhibitory effect on the sodium/potassium pump and an increase in the intraerythrocytic sodium. Such data show the existence in hypertensive subjects of an interrelationship between adrenergic activity and sodium transport systems that could cooperate in causing and/or in maintaining the hypertensive syndrome.

[Effect of beta blockade on the erythrocyte transport of Na+: evaluation during stimulation by cold pressure test in patients with essential hypertension]. / Effetti del beta-blocco sui sistemi di trasporto eritrocitario del Na+: valutazione durante stimolo con cold pressor test in pazienti con ipertensione essenziale.

Several studies have shown in essential hypertension alterations of the transmembrane red blood cells sodium fluxes, as an involvement, especially in the early phases, also of the adrenergic system. In this study we evaluated the behaviour of red blood cells fluxes of sodium before, during and after the cold pressor test, a method used also to evoke an adrenergic stimulation, in twenty hypertensive subjects, 14 males and 6 females, with an average age of 43.2 +/- 5.7 years, with normal weight and without cardiovascular complications and metabolic diseases. The behaviour of the Na+ total efflux (Na+ TE), of the Na+/K+ pump, of the Na+K+ cotransport (Na+/K+ CT), of the Na+/Li+ counter transport (Na+/Li+ Cnt), of the Na+ passive permeability (Na+ PP), of the intracellular Na+ (I Na+) and of the plasmatic noradrenaline (NE) was evaluated basally, at the third minute during cold pressor test (CPT) and 20 minutes after the end of the test. The test, which the same method, was repeated after a 30 day treatment with propranolol at the dose of 240 mg/day in three daily administrations. The beta-blockade caused, besides the reduction of both the systolic and diastolic pressure values, a significant increase in the Na+/K+ CT (from 248 +/- 41 to 314 +/- 71 mmol/l/cells/h, p < 0.001) and a decrease in the Na+ PP (from 0.039 +/- 0.004 to 0.023 +/- 0.007 hr-1, p < 0.00001), probably directed towards the reduction of the accumulation of intracellular Na+, that could compete, among the other mechanisms, with the anti-hypertensive action of the beta-blockers. The CPT caused, before the beta-blockade, a significant depression of the Na+/K+ pump (from 2057 +/- 149 to 1610 +/- 101 mmol/l/cells/h, p < 0.00001) and of the Na+ TE (from 2640 +/- 397 to 2032 +/- 179 mmol/l/cells/h, p < 0.00001) inversely correlated to the levels of NE (r = -0.60, p < 0.003), with a consequent increase in I Na+ (from 6.2 +/- 0.6 to 7.5 +/- 1.5 mmol/l/cells, p < 0.001), showing how the adrenergic activation in hypertensive subjects is able to interfere with the systems of transmembrane transport with an inhibitory attitude, that is expressed by an increase in the levels of I Na+. The beta-blockade was able to outweigh the depression of the Na+/K+ pump (from 1843 +/- 584 to 1728 +/- 640 mmol/l/cells/h, p: ns) and the reduction of the Na+ TE, preventing the accumulation of I Na+ (from 6.3 +/- 1.6 to 6.6 +/- 1.3 mmol/l/cells, p: ns). Such data show an increased susceptibility of the Na+ transport systems to the adrenergic stimuli in hypertensive subjects with a tendency to favor the accumulation of I Na+ and that the beta-blockade is able to antagonize the effects, with a maintenance of the intracellular levels of Na+.

[Clinical-instrumental evaluation of the effects of quinapril treatment in mild-to-moderate hypertension]. / Valutazione clinico-strumentale degli effetti di un trattamento con quinapril nell'ipertensione lieve-moderata.

Eleven patients with uncomplicated mild-to-moderate hypertension (diastolic pressure 95-115 mmHg) were treated for four weeks with daily single quinapril doses of 20-40 mg. Already during the second week a significant reduction in blood pressure was observed without increase of heart rate; 27.3% of patients responded to the lower dose (diastolic blood pressure [90 mmHg], and 54.6% responded to the higher dose. Drug treatment led to reduced pressure increase in response to cold stimulation without influencing the adrenergic response both in basal conditions and after cold pressor test. The drug brought about peripheral vasodilatation as shown by increased perfusion index during Doppler ultrasound examination, and improved arterial reactivity with increased perfusion index and reduced recovery time after ischemia. The reduction of angiotensin and aldosterone plasma levels during treatment was not correlated to diminished blood pressure values, indicating that the antihypertensive effect can occur via pathways different from ACE inhibition. Tolerance was excellent as shown both by clinical and laboratory evidence.

Effects of fluvastatin treatment on red blood cell Na+ transport systems in hypercholesterolemic subjects.

This study was performed to ascertain the effects of short-term cholesterol-lowering therapy with fluvastatin on red blood cells Na+ transport systems. Forty familial hypercholesterolemic subjects (FH; 19 men and 21 women) without hypertension or cardiovascular disease were given a placebo for 4 weeks, and then randomized in two groups. Twenty (fluvastatin group) were given fluvastatin (40 mg/day), and the other 20 (placebo group) continued placebo administration. After the placebo period and after 4 and 12 weeks of placebo or fluvastatin treatment, we measured Na+/K+ pump activity, Na+/K+ cotransport (Na+/K+ Ct), Na+/Li+ countertransport (Na+/Li+ Cnt), passive Na+ permeability (Na+PP), and internal Na+ content (Na+i). The same parameters were measured in 23 control subjects (C) with normal cholesterolemic values, who were matched for sex and age. FH had higher Na+/Li+ Cnt values than C (193.2 +/- 59.4 vs. 139.8 +/- 48.7 microM cells/h; p < 0.01), an increase in Na(+)PP (0.034 +/- 0.012/h vs. 0.018 +/- 0.004/h; p < 0.001), and higher Na(+)i (7.5 +/- 1.5 vs. 6.2 +/- 0.9 mM cells; p < 0.001). In hypercholesterolemic subjects, Na(+)i values were correlated with cholesterol (total and LDL) and apo B levels, whereas an inverse correlation was found for HDL-c and apo AI levels. Reduced total and LDL cholesterol and apo B levels after fluvastatin treatment caused a decrease in both Na(+)/Li(+) Cnt (from 186.1 +/- 60.5 to 125.1 +/- 34.0 microM cells/h; p < 0.001) and Na(+) PP (from 0.035 +/- 0.013/h to 0.02 +/- 0.016/h; p < 0.01), and an increase in Na+/K+ pump activity (from 1,549.0 +/- 507.7 to 1,894.2 +/- 536.2 microM cells/h; p < 0.04), with a significant reduction in the internal Na+ content (from 7.5 +/- 1.6 to 5.8 +/- 2.4 mM cells; p < 0.001). Our findings show that hypercholesterolemia affects red blood cell Na+ transport systems, with an increase in Na+/Li+Cnt, Na+PP, and the internal Na+ content. Cholesterol-lowering treatment with fluvastatin influences Na+ transport systems and reduces the internal Na+ content. This might also be responsible for the greater vascular reactivity observed in hypercholesterolemic patients, and its amelioration after a reduction in cholesterol levels.

Effects of cloricromene on the levels of endothelin and on the microcirculatory function in peripheral atherosclerotic arteriopathies.

The effects of cloricromene on plasma endothelin-1 (ET-1) levels and on microcirculatory function in 9 patients with peripheral atherosclerotic arteriopathy (PAA) and in healthy control subjects were studied. ET-1 levels and microcirculatory function were evaluated both under basal conditions and 30, 60, and 90 min after acute administration of cloricromene (30 mg i.v.). PAA patients had significantly increased levels of ET-1 and impaired vascular parameters (studied by means of Winsor's Index, Gosling's Index, postischemic perfusion index and recovery time) when compared to control subjects. The acute administration of cloricromene (30 mg i.v.) did not change plasma ET-1 both in control subjects and in patients with PAA. In contrast, cloricromene produced a significant improvement in the postischemic perfusion index and in recovery time in arteriopathic patients. Control subjects and patients with PAA also underwent a cold pressor test (CPT) under basal conditions and (72 h later) 30 min after an acute intravenous administration of cloricromene (30 mg i.v.). CPT caused a higher increase in ET-1 in the patients with PAA compared to the control group, and a reduction in the vascular flow at the femoral level, while the pretreatment with cloricromene prevented both the increase in the levels of ET-1 and the reduction of the femoral vascular flow observed after the cold stimulus in patients with PAA. Our data show that cloricromene, besides ameliorating the microcirculatory function, is able to interfere with dynamic mechanisms, such as those induced by the CPT, capable of stimulating the release of ET-1 at the vascular level.