Ischemic injury and experimental transplantation atherosclerosis.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
K Kjeldsen
Publications and source records attributed to K Kjeldsen.
No adaptation to digitalization as evaluated by digitalis receptor (Na,K-ATPase) quantification in explanted hearts from donors without heart disease and from digitalized recipients with end-stage heart failure.
Speculations about development of tolerance to the inotropic effect of digitalis have been engendered since studies in various in vitro systems and tissues not representative of the heart have shown up-regulation of sodium potassium adenosine triphosphatase (Na,K-ATPase) when exposed to digitalis. Moreover the digitalis receptor (i.e., Na,K-ATPase) concentration in the normal, vital human left ventricle has not been previously determined. On this basis, digitalis receptor concentration was quantified in the left ventricle of explanted hearts from subjects without heart disease and from patients with end-stage heart failure who had received digitalis therapy. This was performed using vanadate-facilitated 3H-ouabain binding to intact tissue samples giving values of 728 +/- 58 (n = 5) and 467 +/- 55 pmol/g wet weight (n = 6) (mean +/- SEM) (p < 0.005), respectively. However, some of the digitalis receptors may have retained digoxin before 3H-ouabain binding and thus may have escaped detection. To eliminate this effect of retained digoxin, samples were exposed to prolonged washing in buffer containing excess digoxin antibody, a method recently shown to clear digoxin from receptors and allow subsequent complete digitalis receptor quantification by 3H-ouabain binding. After washing in digoxin specific antibody, specific digitalis receptor concentration was 760 +/- 58 pmol/g (n = 5) and 614 +/- 47 pmol/g (n = 6) wet weight in samples of the normal and failing hearts, respectively (p < 0.08). Thus, digitalization was associated with occupancy of digitalis receptors in the failing human heart of 24% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Human skeletal muscle digitalis glycoside receptors (Na,K-ATPase)--importance during digitalization.
The aims of the present study were to evaluate in humans the putative importance of skeletal muscle digitalis glycoside receptors (Na,K-ATPase) in the volume of distribution of digoxin and to assess whether therapeutic digoxin exposure might cause digitalis receptor upregulation in skeletal muscle. Samples of the vastus lateralis were obtained postmortem from 11 long-term (9 months to 9 years) digitalized (125-187.5 micrograms daily) and eight undigitalized subjects. In intact samples from digitalized patients, vanadate-facilitated 3H-ouabain binding increased 15% (p < 0.02) from 150 +/- 18 to 173 +/- 13 pmol/g wet wt. (mean +/- SEM) after clearing receptors of bound digoxin by washing samples in excess specific digoxin antibody fragments. 3H-ouabain binding in the untreated group was 257 +/- 28 and 274 +/- 26 pmol/g wet wt. (7%, p > 0.30) before and after washing in specific digoxin antibody fragments, respectively. Thus, the present study indicates a approximately 13% occupancy of skeletal muscle digitalis glycoside receptors with digoxin during digitalization. In light of the large skeletal muscle contribution to body mass, this indicates that the skeletal muscle Na,K-ATPase pool constitutes a major volume of distribution for digoxin during digitalization. The results gave no indication of skeletal muscle digitalis glycoside receptor upregulation in response to digoxin treatment. On the contrary, there was evidence of significantly lower (37%, p < 0.005) digitalis glycoside receptor concentration in the vastus lateralis of the digitalized patients, which may be of importance for skeletal muscle incapacity in heart failure.
Aged↗
Effect of testosterone on atherogenesis in cholesterol-fed rabbits with similar plasma cholesterol levels.
The aim was to examine the effect of testosterone on atherogenesis in cholesterol-fed, castrated male rabbits not mediated via different plasma cholesterol levels. The rabbits in the testosterone group (n = 19) and in the placebo group (n = 17) were injected intramuscularly twice weekly for 17 weeks with 25 mg testosterone enantate and placebo, respectively, reaching plasma testosterone levels of 50-150 nmol/l in the testosterone group. No effect of testosterone on liver function or body weight was detected, but at week 15 mean blood pressure was 75 +/- 2 mmHg (mean +/- S.E.) in the testosterone group compared with 69 +/- 2 mmHg in the placebo group (P < 0.05). To reduce variation in plasma cholesterol between the two groups, the amount of cholesterol fed to each rabbit was adjusted on the basis of weekly determinations of plasma cholesterol; the mean plasma cholesterol levels during the 17 weeks were 20.9 +/- 1.0 and 20.4 +/- 0.9 mmol/l for the placebo and testosterone groups. In the intima-inner medias of the aortic arch, the thoracic and the abdominal aorta there were no consistent significant differences in aortic cholesterol content, expressed either as nmol/cm2 or nmol/mg protein, between the two groups. However, the aortic cholesterol content tended to be lower in the testosterone group than in the placebo group. These findings suggest that in cholesterol-fed, castrated male rabbits, testosterone does not promote atherogenesis by an effect directly on the arterial wall.
Animals↗
Aortic esterified cholesterol is not superior to total cholesterol as a measure of atherosclerosis severity in cholesterol-fed rabbits.
Explore the source record for details and available documents.
Animals↗
Effect of lovastatin on cholesterol absorption in cholesterol-fed rabbits.
The aim of the present study was to investigate the effect of the hydroxymethylglutaryl (HMG)-CoA reductase inhibitor lovastatin on some aspects of cholesterol metabolism in cholesterol-fed rabbits. The plasma cholesterol concentration was markedly lower in lovastatin-treated rabbits (6 mg/rabbit/day) compared to controls after 36 days of cholesterol-feeding (x +/- S.E.) (19 +/- 4 mmol/l, n = 9 versus 153 +/- 17 mmol/l, n = 7) (P < 0.00001). Intestinal absorption of cholesterol in such rabbits was reduced by 15% in lovastatin-treated rabbits (n = 21) compared to controls (n = 18) (P < 0.025). The results suggest that the hypocholesterolaemic effect of lovastatin in cholesterol-fed rabbits is associated with a decreased intestinal absorption of cholesterol.
Animals↗
Sprint training increases human skeletal muscle Na(+)-K(+)-ATPase concentration and improves K+ regulation.
This study investigated the effects of sprint training on muscle Na(+)-K(+)-adenosinetriphosphatase (ATPase) concentration, plasma [K+] regulation, muscle performance, and fatigue during severe intermittent exercise. Six untrained male subjects underwent intensive cycle-sprint training for 7 wk. Muscle biopsies were taken at rest from the vastus lateralis muscle before and after 7 wk of training and were assayed for Na(+)-K(+)-ATPase concentration using vanadate-facilitated [3H]ouabain binding to intact samples. Before and after the training period, subjects performed four maximal 30-s exercise bouts (EB) on a cycle ergometer, each separated by a 4-min recovery. Arterialized venous blood samples were drawn immediately before and after each sprint bout and were analyzed for plasma [K+]. The work output was significantly elevated (11%) across all four EBs after training. The muscle [3H]ouabain binding site concentration was significantly increased (16%) from 333 +/- 19 to 387 +/- 15 (SE) pmol/g wet wt after training but was unchanged in muscle obtained from three control subjects. Plasma [K+] rose by 1-2 mmol/l with each EB and declined rapidly by the end of each recovery period. The increases in plasma [K+] resulting from each EB were significantly lower (19%) after training. The ratios of rise in plasma [K+] relative to work output during each EB were also significantly lower (27%) after training. The increased muscle [3H]ouabain binding site concentration and the reduced ratio of rise in [K+] relative to work output with exercise are both consistent with improved plasma and skeletal muscle K+ regulation after sprint training.
Adolescent↗
Na,K-ATPase expression in normal and failing human left ventricle.
The expression of the Na,K-ATPase was studied in both normal and failing human myocardium which was collected within 5 min of cardiac explantation in preparation for orthotopic transplantation or at the time of organ harvest. Abundance of mRNA for all three catalytic alpha subunits of the Na,K-ATPase was analyzed in samples from patients with end-stage heart failure due to either ischemic or dilated cardiomyopathy, as well as from normal controls. Vanadate facilitated 3H-ouabain binding before and after a Digibind wash was analyzed on tissue from a subset of these patients. mRNA analysis demonstrated that all three catalytic Na,K-ATPase alpha subunits were expressed in human heart and that there was no evidence for change in relative expression or abundance induced by disease. The specific digitalis receptor concentration was 760 +/- 58 and 614 +/- 47 pmol/g wet weight in the samples from normal and failing hearts, respectively (p = NS). From these studies it can be concluded that, whereas there is a tendency for a decrease in the number of ouabain receptors in heart failure, there is no significant alteration in the expression of Na,K-ATPase message or protein caused by chronic heart failure.
Binding Sites↗
Quantification of rat cerebral cortex Na+,K(+)-ATPase: effect of age and potassium depletion.
Na+,K(+)-ATPase concentration in rat cerebral cortex was studied by vanadate-facilitated [3H]ouabain binding to intact samples and by K(+)-dependent 3-O-methylfluorescein phosphatase activity determinations in crude homogenates. Methodological errors of both methods were evaluated. [3H]Ouabain binding to cerebral cortex obtained from 12-week-old rats measured incubating samples in buffer containing [3H]ouabain, and ouabain at a final concentration of 1 x 10(-6) mol/L gave a value of 11,351 +/- 177 (n = 5) pmol/g wet weight (mean +/- SEM) without any significant variation between the lobes. Evaluation of affinity for ouabain was in agreement with a heterogeneous population of [3H]ouabain binding sites. K(+)-dependent 3-O-methylfluorescein phosphatase activity in crude cerebral homogenates of age-matched rats was 7.24 +/- 0.14 (n = 5) mumol/min/g wet weight, corresponding to a Na+,K(+)-ATPase concentration of 12,209 +/- 236 pmol/g wet weight. It was concluded that the present methods were suitable for quantitative studies of cerebral cortex Na+,K(+)-ATPase. The concentration of rat cerebral cortex Na+,K(+)-ATPase showed approximately 10-fold increase within the first 4 weeks of life to reach a plateau of approximately 11,000-12,000 pmol/g wet weight, indicating a larger synthesis of Na+,K+ pumps than tissue mass in rat cerebral cortex during the first 4 weeks of development. K+ depletion induced by K(+)-deficient fodder for 2 weeks resulted in a slight tendency toward a reduction in K+ content (6%, p > 0.5) and Na+,K(+)-ATPase concentration (3%, p > 0.4) in cerebral cortex, whereas soleus muscle K+ content and Na+,K(+)-ATPase concentration were decreased by 30 (p < 0.02) and 32% (p < 0.001), respectively. Hence, during K+ depletion, cerebral cortex can maintain almost normal K+ homeostasis, whereas K+ as well as Na+,K+ pumps are lost from skeletal muscles.
Aging↗
Immunity against diphtheria and tetanus in human immunodeficiency virus-infected Danish men born 1950-59.
To evaluate the possible need for vaccination against diphtheria and tetanus of patients infected with the human immunodeficiency virus (HIV), antibodies were measured in blood samples from 78 Danish HIV-infected men, born 1950-59, who could be expected to have received primary vaccination before they contracted the HIV infection. No patients (95% confidence interval: 0-4) had tetanus antibodies below the protective level, whereas 24 of the 78 patients (16-33) were unprotected against diphtheria. In the background population of the same age group and sex, 5% and 10% have been found unprotected against tetanus and diphtheria, respectively. No relationship between disease stages and antibody levels could be found. Neither was there any difference between patients with normal and reduced numbers of CD4+ lymphocytes. From 25 patients two blood samples were taken at an interval of at least one year. Anti-tetanus titres showed a decrease comparable to that found in the background population, whereas the change in anti-diphtheria titres was more variable with rising antibody concentrations in nine patients. The fall off in antibodies did not increase with progression of the disease. It is concluded that HIV-positive younger men who have followed the vaccination program against tetanus prior to the HIV infection can be expected to be protected, whereas revaccination against diphtheria must be considered.
Adult↗
Aortic permeability to LDL as a predictor of aortic cholesterol accumulation in cholesterol-fed rabbits.
The aim of this study was to investigate the possibility that the permeability characteristics of the arterial wall are related to the development of atherosclerosis. The in vivo regional variation of aortic permeability to iodinated human low density lipoprotein (LDL) in normal rabbits was compared with the regional variation in aortic cholesterol accumulation in cholesterol-fed rabbits. Aortas were divided into the aortic arch, thoracic aorta, and abdominal aorta, and each of these three parts was further subdivided into four segments of similar size. The permeability to LDL was 40 +/- 7 nl.cm-2.hr-1 (mean +/- SEM, n = 11) in the most proximal segment of the aortic arch and decreased throughout the length of the aorta to 3 +/- 1 nl.cm-2.hr-1 in the most caudal segment of the abdominal aorta. In such normal rabbits the aortic cholesterol content was similar in all 12 arterial segments at 0.08 +/- 0.005 mumol/cm2 (mean +/- SEM, n = 3 x 12). Aortic cholesterol accumulation was determined in other rabbits with an average plasma cholesterol level of 32 +/- 1 mmol/l for 96 days; the cholesterol content in the most proximal segment of the aortic arch was 2.7 +/- 0.5 mumol/cm2 (mean +/- SEM, n = 11) and decreased with increasing distance from the heart to 0.17 +/- 0.03 mumol/cm2 in the most caudal segment of the abdominal aorta. Linear regression analysis showed a close positive association between the permeability to LDL of a given aortic segment and the cholesterol accumulation in that same aortic segment after cholesterol feeding (r2 = 0.96, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Interrelation of hypokalaemia and potassium depletion and its implications: a re-evaluation based on studies of the skeletal muscle sodium, potassium-pump.
Explore the source record for details and available documents.
Homeostasis↗
No upregulation of digitalis glycoside receptor (Na,K-ATPase) concentration in human heart left ventricle samples obtained at necropsy after long term digitalisation.
STUDY OBJECTIVE: The aim was to evaluate the hypothesis that digitalis glycosides increase the concentration of their specific receptor (Na,K-ATPase) in human myocardial tissue, thereby possibly reducing the inotropic effect of long term digitalis treatment. DESIGN: Intact samples of left ventricle were obtained at necropsy from patients who had been on long term treatment with digoxin and from patients not previously given digoxin. Digitalis glycoside receptors were quantified using vanadate facilitated 3H-ouabain binding before and after washing samples in buffer containing excess digoxin antibody fragments for 16 h at 30 degrees C. This washing procedure has previously been shown to reduce prior specific digoxin binding in human left ventricle by 95% and to allow subsequent vanadate facilitated complete quantification of 3H-ouabain binding sites. In this context it was performed to reduce occupancy of digitalis glycoside receptors by digoxin, caused by digitalisation before 3H-ouabain binding. SUBJECTS: 11 patients who had been on long term treatment with digoxin and eight who had not previously been given digoxin were studied. Left ventricle samples were obtained at necropsy at around 15 h after death. MEASUREMENTS AND MAIN RESULTS: Standard 3H-ouabain binding was 39% less in samples from digitalised than from undigitalised subjects (p less than 0.001). Washing samples in buffer containing excess digoxin antibody fragments induced an increase in 3H-ouabain binding from 174(SEM 10) to 265(20) pmol.g-1 wet weight (n = 11, p less than 0.001) in samples from digitalised patients. After washing, the digitalis glycoside receptor concentration in left ventricle samples showed a tendency to a lower value (14%, p greater than 0.10) in patients exposed to digoxin compared to left ventricle samples from individuals unexposed to digitalis glycoside treatment. Calculating 3H-ouabain binding relative to dry ventricular muscle weight confirmed the results obtained using wet weight as reference. CONCLUSIONS: The results suggest that digoxin treatment in life is associated with a 34% occupancy of digitalis glycoside receptors with digoxin. In the human heart there was no evidence for upregulation of digitalis glycoside receptor concentration due to long term digitalisation. Thus at receptor level there was no evidence for development of tolerance to digoxin therapy. The lower digitalis glycoside receptor concentration in the left ventricle observed in the heart failure patients may support the report of a relationship between Na,K-ATPase concentration as evaluated by 3H-ouabain binding and left ventricular function.
Aged↗
Enhanced clearance of specifically bound digoxin from human myocardial and skeletal muscle samples by specific digoxin antibody fragments: subsequent complete digitalis glycoside receptor (Na,K-ATPase) quantification.
The effect of digoxin antibody fragments (Fab) on clearance of specifically bound digoxin from its specific receptor (Na, K-ATPase) was studied in human heart left ventricle (LV) and vastus lateralis skeletal muscle (SK) samples obtained postmortem. Initially, [3H]digoxin was bound to samples at conditions giving high relative occupancy of receptor. Half-life (t1/2) for its net release from LV in buffer was 32.2, 6.7, and 0.9 h at 0 degrees, 30 degrees, and 37 degrees C, respectively. For SK, t1/2 was 5.4 h in buffer at 30 degrees C. Inhibition of rebinding of digoxin by addition of specific digoxin Fab (5 x 10(-7) M) or excess unlabeled digoxin (1 x 10(-4) M) to buffer at 30 degrees C increased net release rate for specifically bound digoxin 2.5- to 3.0-fold in heart and SK. [3H]Digoxin was also bound to samples at conditions giving low relative occupancy. Samples were subsequently washed in buffer containing 5 x 10(-7) M specific digoxin Fab for 16 h at 30 degrees C. This wash reduced occupancy of receptors by digoxin from 10 to 0.5% in LV and from 9 to 0.3% in SK, respectively. At variance with wash at 37 degrees C, this procedure allowed subsequent vanadate-facilitated complete quantification of Na,K-ATPase by [3H]ouabain binding; values were 378 +/- 13 and 370 +/- 12 pmol/g wet weight (p greater than 0.6) in LV and 309 +/- 19 and 315 +/- 16 pmol/g wet weight (p greater than 0.7) in SK with and without previous wash, respectively (mean +/- SEM, n = 12).(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Muscle Na,K-pump dysfunction may expose the heart to dangerous K levels during exercise.
During exercise, potassium leaks out of muscle cells and interstitial potassium concentration may rise to 15 mmol/l. Potassium is then in part transported back to the cells by the Na,K-pump. The leak of potassium from working human muscles can be calculated to 15 mumol/g/min. Human muscles contain 300 pmol/g wet weight Na,K-pumps and have a maximum capacity for potassium uptake of 5 mumol/g/min. At rest only a small percentage is used, but during maximum stimulation the entire capacity can probably be used. During exercise, total potassium leakage from the human muscle pool is 400 mmol/min and maximum active reuptake capacity is 100 mmol/min. ECV contains only 50 mmol potassium. During heavy exercise the capacity for active potassium uptake in muscle pool may be exceeded and interstitial potassium equilibrates with plasma potassium, which then may rise to 10 mmol/l. Training can decrease the rise in plasma potassium during exercise by 0.2-0.5 mmol/l. Variation in muscle Na,K-pump concentration may be associated with changed plasma potassium homeostasis during exercise, which if disadvantageous may be dangerous to the heart.
Biological Transport, Active↗
The concentration of the Na,K-pump in skeletal and heart muscle in congestive heart failure.
Na,K-ATPase (or the Na,K-pump) is essential for excitability and contractility of muscle tissue. Previous studies have shown a decrease in the concentration of this pump in endomyocardial biopsies from patients with dilated cardiomyopathy. The effect of congestive heart failure on the concentration of Na,K-ATPase in skeletal muscle was assessed in 16 patients by measurement of binding of 3H-ouabain to biopsies of the vastus lateralis muscle. Ten patients had impaired left ventricular function with an ejection fraction of 0.32 +/- 0.03 and a concentration of the Na,K-pump of 229 +/- 15 pmol/g wet weight in the skeletal muscle, whereas 6 patients had an ejection fraction of 0.66 +/- 0.05 (P less than 0.001) and a concentration of 307 +/- 17 pmol/g wet weight (P less than 0.01). In endomyocardial biopsies, the concentration of Na,K-ATPase was 340 +/- 37 and 500 +/- 39 pmol/g wet weight (P less than 0.025) in patients with impaired and normal ventricular function, respectively. There was a significant correlation between the concentration of the Na,K-pump in the biopsies of the skeletal muscle and ejection fraction, as well as between its concentration in the endomyocardial and skeletal muscular biopsies (r = 0.56, P less than 0.025 and r = 0.72, P less than 0.005, respectively). The decrease in concentration of the pump in skeletal muscle may contribute to the limitation of exercise capacity in congestive heart failure.
Adult↗
Human skeletal muscle Na, K-ATPase concentration quantified by 3H-ouabain binding to intact biopsies before and after moderate physical conditioning.
The putative effect of moderate training on human skeletal muscle Na,K-ATPase concentration and thus on the capacity for active uptake of potassium was evaluated. In 15 conscripts the Na,K-pump concentration was determined in vastus lateralis muscle by measurement of 3H-ouabain binding to intact muscle biopsies before and after 10 weeks of physical training. All subjects had improved physical fitness, body weight was reduced by 3% (P less than 0.001), Cooper's test showed an improvement by 7% (P less than 0.05) and leg circumference 10 cm above the knee joint had increased by 3% (P less than 0.001). Mean Na,K-pump concentration +/- S.E.M. in vastus lateralis muscles was 308 +/- 13 (N = 15) and 300 +/- 7 (N = 15) pmol x g wet wt.-1 (P less than 0.60) before and after training, respectively. Thus, in human subjects moderate improvement of physical performance may occur without any change in skeletal muscle Na,K-pump concentration. It may be, however, that change in the acute regulation of skeletal muscle Na,K-ATPase--i.e. augmented activity of existing Na,K-pumps--may reduce exercise-induced rise in plasma potassium concentration after moderate physical conditioning. Since the circumference of the legs had increased, the total amount of Na,K-ATPase in the legs had probably increased. Hence, moderate training may induce muscle hypertrophy with a balanced synthesis of muscle mass and Na,K-pumps.
Adolescent↗
Age-dependent change in myocardial cardiac glycoside receptor (Na,K-pump) concentration in children.
Myocardial Na,K-ATPase concentration was quantified in 18 0-8-year-old human subjects by vanadate-facilitated 3H-ouabain binding to intact samples of the left ventricle of the heart obtained at autopsy. Within the first 6 months of life, the Na,K-ATPase concentration showed a rapid decrease. The mean value in the age range from birth to 6 months was 1.6 times the mean value obtained in the age range 6 months to 8 years. The mean values +/- SEM were 1,076 +/- 57 (n = 10) and 671 +/- 28 (n = 8) (p less than 0.001) pmol/g wet weight, respectively. The highest value [1,433 +/- 56 pmol/g wet weight (n = 5)] was found in a 3-month-old child and the lowest value [545 +/- 22 pmol/g wet weight (n = 5)] in an 8-year-old. Evaluation of 3H-ouabain-binding kinetics showed no age-dependent variations. The total amount of Na,K-ATPase found in the heart was approximately 30 and 80 nmol within the first 3 years of life and at 8 years, respectively. The age-dependent change in myocardial Na,K-ATPase concentration can be ascribed to variation in the ratio between the amount of Na,K-ATPase and muscle mass during development. Since myocardial Na,K-ATPase is the receptor for cardiac glycosides, the present results may in part explain the clinical observation that cardiac glycoside sensitivity and toxicity change in young age.
Aging↗