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Biomedical subjects

B O Göbel

Publications and source records attributed to B O Göbel.

18 recordsLinked to original sources

Kinetics of Na+/H+ exchange in vascular smooth muscle cells from WKY and SHR: effects of phorbol ester.

The kinetic properties of Na+/H+ exchange were investigated in vascular smooth muscle cells (VSMC) in culture from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Antiport activity was measured in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein-loaded cells after nigericin-induced cytosolic acidification. Studies were performed without (control) and with pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA; 200 nM). Na+/H+ exchange markedly differed between the two strains with lower Hill coefficients [1.56 +/- 0.17 (SE) vs. 2.62 +/- 0.36] and higher maximal activity (Vmax) values (55.85 +/- 5.24 vs. 31.11 +/- 2.38 mmol H+.l-1.min-1) in SHR compared with WKY cell lines. PMA markedly altered the antiport kinetics in WKY VSMC with a decrease in the Hill coefficient (1.75 +/- 0.14) without affecting Vmax (31.88 +/- 1.55 mmol H+.l-1.min-1). In VSMC from SHR, PMA had no effect on the kinetic variables investigated. Thus two kinetic abnormalities are present with respect to Na+/H+ antiport activity in VSMC from SHR compared with WKY, i.e., increased Vmax and decreased Hill coefficient. The observation that PMA does not affect the kinetics of the Na+/H+ antiport in VSMC from SHR suggests a marked degree of antiporter prestimulation in this animal model of genetic hypertension.

Animals↗

Dependency of overall fractionation effect of respiration on hemoglobin concentration within blood at rest.

In this study it was investigated in which way varying hemoglobin concentrations within blood influence overall fractionation effect of respiration, meaning a change in composition of isotopic oxygen molecules 16O2 and 16O18O within oxygen transported during entire respiration. Since overall fractionation effect of respiration is known to consist of different fractionating and non-fractionating processes, measuring it under condition of anemia could be useful in relating changes in isotopic compositions of oxygen to limitations of entire oxygen transport caused by one or more of these processes. Experiments were performed on 6 patients suffering from various degrees of anemia of a variety of etiologies and on 6 healthy humans. All test subjects breathed air at rest. Samples from inspiratory and expiratory gas were taken in order to analyse 16O18O/16O2 ratios with the aid of respiratory mass spectrometry. Values of overall fractionation effect decreased with respect to a drop in hemoglobin concentration from 17.6 to 6.6 g/100 ml in terms of a linear relationship (r = 0.79) provided that values of overall fractionation effect were normalized so as to exclude the influence of varying ventilatory conditions. It could be shown that at a value of hemoglobin content of 6.6 g/100 ml, 16O2 was transported in preference to 16O18O with a 0.57% higher rate compared to a value of 0.78% obtained at a hemoglobin concentration of 17.6 g/100 ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗

The lymphocyte Na+/H+ antiport: activation in primary hypertension and during chronic NaCl-loading.

Increased activity of the Na+/H+ antiport may be a major abnormality in essential hypertension. The activity of this transport system was investigated in lymphocytes from 13 patients with untreated essential hypertension (Ht) and 13 normotensive control subjects (Nt) on an ad libitum (130-170 mmol d-1) NaCl intake. Furthermore, the effects of different states of NaCl balance on lymphocyte Na+/H+ antiport were evaluated in two groups of Nt volunteers receiving 20 vs. 300 mmol d-1 (n = 8) and 85 vs. 200 mmol d-1 (n = 14) of NaCl for 1 week each and in seven Ht patients (20 vs. 300 mmol NaCl d-1 for 1 week each). Additionally, during the 20 and 300 mmol/d NaCl intake red blood cell membrane transport was studied in eight subjects. For the determination of lymphocyte antiport activity, cells were loaded with the cytosolic pH (pHi) indicator bis-carboxyethyl carboxyfluorescein (BCECF-AM) and acidified by addition of different amounts of Na(+)-propionate (5-40 mM). Initial pHi-recovery was taken as the activity of the antiport system and plotted against pHi-values after acidification. Non-linear regression analysis yielded higher 'apparent' maximal transport rates in Ht than Nt (Nt: 2.00 +/- 0.22; Ht: (3.81 +/- 0.59) x 10(-3) s-1; P < 0.025). In contrast, baseline pHi-values and pHi-values at half-maximal activity (pK) were identical in Nt and Ht. In normotensive control subjects on an NaCl intake of 20, 85, 200 and 300 mmol d-1 for 7 d, 'apparent' maximal transport rates averaged 2.75 +/- 0.20, 2.89 +/- 0.17, 2.81 +/- 0.18 and (3.62 +/- 0.25) x 10(-3) s-1, respectively. Thus, antiport activity was significantly (P < 0.05) stimulated on the 300 mmol d-1 intake as compared to the three other NaCl intakes. The extreme intakes of NaCl (20 vs. 300 mmol d-1) in normotensive volunteers did not affect the erythrocyte Na+/K+ pump, Na+/K+ cotransport and Na+/Li+ countertransport. Our study supports the concept that a group of patients with primary hypertension exhibit an activated Na+/H+ antiport. Furthermore, our data demonstrate that a chronic high intake of NaCl is associated with an increase in lymphocyte antiport activity towards the high values observed in primary hypertension.

Adult↗

Platelet Na+/H+ antiport activity in patients with insulin-dependent diabetes mellitus with and without diabetic nephropathy.

The incidence of diabetic nephropathy in patients with insulin-dependent diabetes mellitus (IDDM) may depend on factors other than the quality of diabetes control. Hypertension is an additional factor associated with a high degree of renal involvement in IDDM. One abnormality consistently observed in various tissues of patients with essential hypertension is enhanced activity of the Na+/H+ antiport. In the present study we have therefore studied platelet antiport activity in 41 healthy subjects (control), in 22 patients with untreated essential hypertension (EH), and in 35 normotensive IDDM patients (type 1). Of these patients 17 exhibited signs of diabetic nephropathy (group 1) while 18 had no evidence for renal involvement of IDDM in spite of a duration of IDDM of at least 10 years (group 2). The two IDDM patient groups were undistinguishable with respect to age, body mass index, and arterial blood pressure (group 1, 117.9 +/- 2.4/78.4 +/- 1.5 mmHg; group 2, 113.9 +/- 3.6/76.1 +/- 1.8 mmHg). Antiporter activity was determined from the rate of cell volume changes induced by propionic acid. Platelet Na+/H+ exchange activity averaged 23.43 +/- 0.43 10(-3).s-1 in control subjects and was markedly elevated in EH (28.38 +/- 0.62 10(-3).s-1; P < 0.01). Antiport activity in group 2 patients without nephropathy averaged 24.54 +/- 0.57 10(-3).s-1 and was undistinguishable from the control group. However, platelet Na+/H+ antiport activity was significantly stimulated in group 1 patients with nephropathy as compared to group 2 (26.95 +/- 0.73 10(-3). s-1; P < 0.025). Our results show that renal involvement in IDDM is associated with enhanced activity of the platelet Na+/H+ antiport.

Adult↗

Efficacy and safety of two different galenic formulations of a transdermal clonidine system in the treatment of hypertension.

The efficacy and safety of two different galenic formulations of transdermal clonidine systems were compared in 905 patients with mild to moderate essential hypertension during a 12 weeks observation period. 449 patients were treated with the matrix controlled clonidine transdermal (C-TD) system and 456 patients with the membrane controlled clonidine system (C-TTS). The mean blood pressure was reduced from 168/102 mmHg to 146/87 mmHg in the C-TD and from 169/102 mmHg to 148/88 mmHg in the C-TTS group. There was no difference in the response rate. The pattern of systemic side-effects appeared to correspond to those seen during oral clonidine treatment but with a lower frequency and intensity. The C-TD patch improved skin tolerability and the drop-out rate due to skin reactions was 2.2 times lower compared with the C-TTS group. Local skin reactions led to withdrawal in 35 of 449 C-TD treated and in 79 of 456 C-TTS treated patients. In conclusion, the improved carrier system for the transdermal clonidine treatment reduced local side-effects which in turn may further enhance acceptability and compliance in treated patients.

Administration, Cutaneous↗

Inhibition of cyclooxygenase attenuates baroreceptor function and increases the pressor response to norepinephrine in man.

The possible influence of prostaglandins on baroreceptor function in man has been investigated. Baroreceptor reflex was activated by intravenous infusion of norepinephrine and the pressor response was measured, both before and after administration of indomethacin. Resting blood pressure remained unchanged after indomethacin while resting heart rate was significantly decreased as compared to placebo and the norepinephrine-induced rise in mean arterial blood pressure was significantly more pronounced. The baroreceptor-mediated decrease in heart rate tended to be smaller. Baroreceptor sensitivity (delta heart rate/delta blood pressure) was significantly reduced by indomethacin to about half of the control value. In addition to attenuation of sensitivity, the findings represent resetting of the baroreceptor setpoint and a more pronounced pressor response to norepinephrine after cyclooxygenase inhibition. Thus, eicosanoids originating via the cyclooxygenase pathway of arachidonate metabolism may modulate the vascular response to adrenergic stimulation and may participate in the regulation of baroreceptor reflex setpoint and sensitivity.

Adult↗

Platelet cAMP and cGMP in essential hypertension.

Vasodilator substances released in the blood vessel wall, such as the endothelium-derived relaxing factor (EDRF) and prostacyclin (PGI2), may participate in the regulation of arterial blood pressure. However, their role in the pathogenesis of human essential hypertension to date remains unclear. For some of these factors affecting vascular smooth muscle cells, blood platelets represent a second target tissue. Thus, EDRF and PGI2 inactivate platelets by stimulation of cyclic guanosine-5'-monophosphate (cGMP) and cyclic adenosine-5'-monophosphate (cAMP) synthesis, respectively. In the present study, platelet cAMP (n = 68) and cGMP (n = 60) were determined in a control group of healthy subjects (C) and in 12 patients with untreated essential hypertension (EH). In the control group, platelet cAMP and cGMP content averaged 13.52 +/- 0.38 and 1.48 +/- 0.06 pmol/10(9) platelets and no dependence of either variable on sex or age could be established. Furthermore, cGMP levels were similar in EH as compared to the control group (1.38 +/- 0.11 pmol/10(9) platelets). However, intracellular concentrations of cAMP were significantly lower in EH as compared to C (11.22 +/- 1.37 pmol/10(9) platelets; P < .01). In addition, we investigated the stimulatory effect on cAMP of the stable PGI2 analog iloprost (10(-9), 5 x 10(-9), 10(-8), 5 x 10(-8) mol/L) in the platelets of 12 control subjects (C12) and EH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Membrane transport, sodium balance, and blood pressure regulation.

Essential hypertension is characterized by polygenic inheritance and quantitative and/or qualitative abnormalities of membrane transport systems may function as intermediate phaenotypes. The present review attempts to evaluate the importance of sodium transport systems such as the sodium pump, cotransport and countertransport as aetiological or pathogenetic factors involved in primary hypertension. Furthermore, the relative importance of NaCl balance as an exogenous factor modifying these transport systems is reviewed. Controversial results exist with respect to the activity of the sodium pump and cotransport both as a function of blood pressure and NaCl balance. In contrast, accumulating evidence suggests that the activity of the counter-transport system is increased in essential hypertension and that this may be observed even before the elevation of blood pressure can be documented. In own studies performed in normotensive volunteers on a low (20 mmol/day) and high (320 mmol/day) NaCl intake, lymphocyte antiport activity was significantly higher during chronic NaCl loading. Therefore, alterations of the Na+/H+ antiport system may represent an intermediate phaenotype of gene(s) involved in the genesis of primary hypertension. Preliminary evidence suggests that NaCl balance may be an exogenous modulator of this system.

Animals↗

Arterial blood pressure. Correlation with erythrocyte count, hematocrit, and hemoglobin concentration.

The relationship between arterial blood pressure and red blood cell variables was investigated in 1013 unselected persons with a blood pressure range of 90 to 225 mm Hg systolic and 50 to 145 mm Hg diastolic. Statistically significant correlations were demonstrated between mean (as well as systolic and diastolic) arterial blood pressure and red blood cell count (r = 0.27; P less than .0001), hematocrit (r = 0.28; P less than .0001), and hemoglobin concentration (r = 0.29; P less than .0001). Average arterial blood pressure was higher in men than in women (133 +/- 16/83 +/- 10 v 124 +/- 16/79 +/- 9 mm Hg, P less than .0001) and this was associated with higher values for erythrocyte count, hemoglobin concentration, and hematocrit in men as compared to women. The significant correlation of blood pressure and hematocrit, which represents one important determinant of blood viscosity, points to a role for rheological factors in the long-term control of blood pressure. Moreover, it might be speculated that the sex difference in blood pressure as observed in the present study may be due, at least in part, to stimulated erythropoiesis in men as compared to women.

Adult↗

Converting enzyme inhibition and vascular prostacyclin synthesis: effect of kinin receptor antagonism.

The effects of angiotensin I-converting enzyme (ACE) inhibitors and bradykinin (BK) on prostacyclin (PGI2) production in isolated arterial tissue were investigated. Rings of rat abdominal aorta were incubated in Krebs-Ringer bicarbonate buffer and PGI2 generation was assessed by the determination of its stable hydrolysis product; 6-keto-PGF1 alpha. The addition of both ACE inhibitors, captopril and lisinopril, and bradykinin resulted in dose-dependent stimulation of PGI2 biosynthesis when the individual substance was added into the incubation buffer at final concentrations between 10(-8) and 10(-5) M. The bradykinin-induced stimulation of PGI2 synthesis was dose dependently inhibited by the BK receptor antagonist, D-Arg[Hyp3, Thi5,8, D-Phe7]BK. The captopril- and lisinopril-induced stimulation of vascular 6-keto-PGF1 alpha production was also significantly decreased when the BK antagonist was added to the incubation medium together with the ACE inhibitors. Our results show that both captopril and lisinopril stimulate PGI2 synthesis in arterial tissue and that this effect may be secondary to changes in the activity of the kinin system.

6-Ketoprostaglandin F1 alpha↗

Effects of n-3 fatty acids on renal function and renal prostaglandin E metabolism.

The present study was performed to investigate the effects of dietary fish oil supplements on renal function and renal prostaglandin (PG) E metabolism. The usual "western" diet of 10 healthy volunteers (six female and 4 male) aged between 21 and 35 years was supplemented with 6 g/day of n-3 polyunsaturated fatty acids [3.6 g of eicosapentaenoic acid (EPA) and 2.4 g of docosahexaenoic acid (DHA)] for six weeks. Supine arterial blood pressure (BP) and heart rate (HR), renal hemodynamics, renal excretory function and urinary excretion of PGE2 and PGE3 were determined before and at the end of the fish oil supplementation period. No changes could be observed in BP and HR while renal plasma flow (RPF), determined as the clearance of PAH, significantly increased from 559 +/- 44 to 738 +/- 47 ml/min (P less than 0.001) with the fish oil supplements. This was associated with a decrease in renal vascular resistance from (8.11 +/- 0.54).10(-2) to (6.37 +/- 0.38).10(-2) mm Hg.min.ml-1 (P less than 0.01). Glomerular filtration rate (GFR), determined as the clearance of inulin, increased from 97 +/- 3 to 107 +/- 3 ml/min (P less than 0.01), resulting in a decrease in filtration fraction from an average of 0.19 +/- 0.01 to 0.15 +/- 0.01 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Fish oil and baroreceptor function in man.

The present study was designed to investigate the effects of dietary fish oil supplements on blood pressure, the pressor response to norepinephrine, and sensitivity of the arterial baroreceptor reflex. 10 normotensive volunteers (six female and 4 male) aged between 21 and 35 years were given 6 g/day of n-3 polyunsaturated fatty acids (3.6 g of eicosapentaenoic acid and 2.4 g of docosahexaenoic acid) during six weeks in addition to their usual diet. Resting blood pressure (BP), blood pressure response to exogenous norepinephrine (NE), and changes in heart rate (HR) associated with the blood pressure increase during NE infusion were determined before and at the end of the fish oil supplementation period. No changes in BP could be observed following the n-3 fatty acid supplements as compared to control values (110.7 +/- 2.4/63.5 +/- 2.9 mmHg vs. 110.6 +/- 1.9/60.1 +/- 1.3 mmHg). Blood pressure values during infusion of 0.1 micrograms/kg body weight of NE were 119.8 +/- 2.4/67.4 +/- 1.7 mmHg before the fish oil supplementation period and were also unchanged (119.9 +/- 2.0/70.5 +/- 1.9 mmHG) after the fish oil diet. HR during NE infusion was significantly (p less than 0.01) more suppressed after the fish oil supplementation period. During control, HR decreased in parallel with the rise in blood pressure from 69.2 +/- 2.8 min-1 to 63.9 +/- 2.4 min-1 (difference of 5.3 +/- 0.5 min-1), while after the fish oil supplementation HR fell from 68.1 +/- 3.5 min-1 to 56.2 +/- 2.6 min-1 (difference of 11.9 +/- 1.5 min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Role of the furosemide-sensitive Na+/K+ transport system in determining the steady-state Na+ and K+ content and volume of human erythrocytes in vitro and in vivo.

To study the physiological role of the bidirectionally operating, furosemide-sensitive Na+/K+ transport system of human erythrocytes, the effect of furosemide on red cell cation and hemoglobin content was determined in cells incubated for 24 hr with ouabain in 145 mM NaCl media containing 0 to 10 mM K+ or Rb+. In pure Na+ media, furosemide accelerated cell Na+ gain and retarded cellular K+ loss. External K+ (5 mM) had an effect similar to furosemide and markedly reduced the action of the drug on cellular cation content. External Rb+ accelerated the Na+ gain like K+, but did not affect the K+ retention induced by furosemide. The data are interpreted to indicate that the furosemide-sensitive Na+/K+ transport system of human erythrocytes mediates an equimolar extrusion of Na+ and K+ in Na+ media (Na+/K+ "cotransport"), a 1:1 K+/K+ (K+/Rb+) and Na+/Na+ "exchange" progressively appearing upon increasing external K+ (Rb+) concentrations to 5 mM. The effect of furosemide (or external K+/Rb+) on cation contents was associated with a prevention of the cell shrinkage seen in pure Na+ media, or with a cell swelling, indicating that the furosemide-sensitive Na+/K+ transport system is involved in the control of cell volume of human erythrocytes. The action of furosemide on cellular volume and cation content tended to disappear at 5 mM external K+ or Rb+. The in vivo red cell K+ content was negatively correlated to the rate of furosemide-sensitive K+ (Rb+) uptake, and a positive correlation was seen between mean cellular hemoglobin content and furosemide-sensitive transport activity. The transport system possibly functions as a K+ and water-extruding mechanism under physiological conditions in vivo. The red cell Na+ content showed no correlation to the activity of the furosemide-sensitive transport system.

Biological Transport↗

Na+-K+ transport and volume of rat erythrocytes under dietary K+ deficiency.

Red cell Na+ and K+ content and transport were studied in Sprague-Dawley rats in the course of a dietary K+ depletion ranging 1-6 wk. Plasma K+ fell to below 2 mM, and red cell K+ decreased. Cellular Na+ rose due to an increase of the Na+ leak. Inward Rb+ and outward Na+ transport by the Na+-K+ pump (determined at 2 mM external Rb+) were accelerated by the rise in cell Na+ concentration. K+ depletion caused a cation deficit of up to 30% of total red cell Na+ plus K+ and a consecutive cell shrinkage with an increase in mean cellular hemoglobin content (MCHC). The cell shrinkage, in turn, was paralleled by up to a 10-fold increase in the maximum capacity of the furosemide-sensitive, chloride-dependent Na+-K+ cotransport system. This system participated with up to 50% of the total K+ movements across the red cell membrane in severe K+ deficiency. In normal cells shrunken by osmotic means, Na+-K+ cotransport was similarly accelerated severalfold, indicating that the cell shrinkage occurring during K+ depletion is a major factor inducing the changes in Na+-K+ cotransport. However, a second unknown factor is also involved. It is concluded that in the rat, not only genetic but also environmental parameters contribute in determining the actual activity of the red cell Na+-K+ cotransport system. The cell volume and MCHC must be considered when judging Na+ and K+ transport changes observed in rat erythrocytes under various pathophysiological conditions.

Animals↗

Sodium-lithium exchange and sodium-potassium cotransport in human erythrocytes. Part 1: Evaluation of a simple uptake test to assess the activity of the two transport systems.

A reliable and simple uptake test is proposed to assess the activity of the sodium lithium (Na+-Li+) countertransport and the sodium-potassium (Na+-K+) cotransport system of human erythrocytes. The test consists in measurement of phloretin-sensitive Li+ uptake from magnesium (Mg2+) media containing 2 mM Li+ and of furosemide-sensitive rubidium (Rb+) uptake from Na+ media containing 5 mM Rb+. Both Li+ and Rb+ are determined by atomic absorption spectrophotometry. The particular experimental conditions of the uptake assay are analyzed with respect to parameters that potentially affect the results, such as pH, cell volume, internal Na+, external Na+ and Rb+, presence of other ions, and concentration and protein-binding of furosemide, respectively. It is found that the activity of the two transport systems varies more than threefold among normotensive individuals, the activities in erythrocytes of each individual donor remaining stable within +/- 10% over more than two red cell life spans. The Li+ and Rb+ uptake rates are highly correlated to Li+ and K+ or Na+ release rates as determined by the methods of Canessa et al. and Garay et al. The test can thus be applied for routine screening in the search of "abnormalities" of red cell cation transport in hypertensive patients.

Biological Transport↗

Sodium-lithium exchange and sodium-potassium cotransport in human erythrocytes. Part 2: A simple uptake test applied to normotensive and essential hypertensive individuals.

The sodium-lithium (Na+-Li+) exchange and sodium-potassium (Na+-K+) cotransport activities were assessed on erythrocytes of 38 normotensive individuals, 18 patients with well-established essential hypertension, and five renal hypertensive patients, by means of an uptake assay method. With both transport systems, no significant differences in mean values and variance were observed among the three groups. Four of six low-renin essential hypertensive patients exhibited some of the lowest exchange and cotransport rates obtained among all individuals examined. The activity of both transport systems was slightly lower in women than in men.

Adult↗

Sodium and potassium ion transport accelerations in erythrocytes of DOC, DOC-salt, two-kidney, one clip, and spontaneously hypertensive rats. Role of hypokalemia and cell volume.

Sodium (Na+) and potassium (K+) transport by the furosemide-sensitive Na+-K+ transport system, the Na+-K+ pump, and the cation leak(s) were studied in erythrocytes from DOC-water, DOC-salt, two-kidney, one clip (Sprague-Dawley), and spontaneously hypertensive rats (Wistar-Kyoto). Rubidium (Rb+) was used as a tracer for K+. After 4 weeks of DOC-salt hypertension, inward K+ (Rb+) transport by the furosemide-sensitive system was increased threefold, and the inward Na+ leak and the red cell Na+ content were elevated by about 50%. The rise in cell Na+ accelerated K+ inward and Na+ outward transport by the Na+-K4 pump, DOC-water hypertension caused similar but less pronounced changes. In two-kidney, one clip hypertension, the Na+ leak and the Na+-K+ pump rates were slightly elevated, and furosemide-sensitive Rb+ uptake tended to be increased. In spontaneously hypertensive rats, furosemide-sensitive Rb+ uptake was accelerated by 50%. The marked hypokalemia in DOC-water and DOC-salt hypertension was associated with a slight loss of red cell K+ and an increase in mean cellular hemoglobin content (MCHC), indicative of cell shrinkage. Hypokalemia induced by dietary K+ deficiency caused alterations in red cell cation transport, content, and cell volume which were qualitatively similar but more pronounced than those seen in DOC-salt hypertension. Osmotic shrinkage in vitro induced a severalfold acceleration of furosemide-sensitive Rb+ uptake, similar to that observed in rat erythrocytes shrunken in vivo in K+-deficient states. It is concluded that the acceleration of furosemide-sensitive K+ (Rb+) transport in erythrocytes of mineralocorticoid hypertensive rats is largely caused by the hypokalemia and consecutive red cell K+ loss and shrinkage, respectively. Mean cellular hemoglobin content (MCHC) is thus a parameter that must be considered in studies on Na+ and K+ transport across the membrane of rat erythrocytes.

Animals↗