Endogenous Digoxin-like Factor Research Articles

Association of cord blood digitalis-like factor and necrotizing enterocolitis

Endogenous digoxin-like factor (EDLF) has been linked to vasoconstriction, altered membrane transport, and apoptosis. Our objective was to determine whether increased EDLF in the cord sera of preterm infants was associated with an increased incidence of necrotizing enterocolitis (NEC). Cord sera from pregnant women enrolled in a randomized trial of MgSO4 for fetal neuroprotection were analyzed for EDLF using a red cell Rb(+) uptake assay in which the inhibition of sodium pump-mediated Rb(+) transport was used as a functional assay of EDLF. Specimens were assayed blinded to neonatal outcome. Cases (NEC, n = 25) and controls (neonates not developing stage 2 or 3 NEC, n = 24) were matched by study center and gestational age. None of the women had preeclampsia. Cases and controls were compared using the Wilcoxon test for continuous and the Fisher exact test for categorical variables. A conditional logistic regression analysis was used to assess the odds of case vs control by EDLF level. Cases and controls were not significantly different for gestational age, race, maternal steroid use, premature rupture of membranes, or MgSO4 treatment. In logistic models adjusted for treatment group, race, premature rupture of membranes, and gestational age, cord sera EDLF was significantly associated with development of NEC (P = .023). These data demonstrated an association between cord sera EDLF and NEC.

188: Association of cord blood digitalis-like factor and necrotizing enterocolitis in the neonate

Endogenous digoxin-like factor (EDLF) has been linked to vasoconstriction and altered membrane transport. Our objective was to determine if increased EDLF in the cord sera of preterm infants was associated with an increased incidence of intraventricular hemorrhage (IVH) and necrotizing enterocolitis (NEC).

HYPOTHALAMIC DIGOXIN, HEMISPHERIC CHEMICAL DOMINANCE, AND PEPTIC ULCER DISEASE

The isoprenoid pathway produces three key metabolites--endogenous digoxin-like factor (EDLF) (membrane sodium-potassium ATPase inhibitor and regulator of neurotransmitter transport), ubiquinone (free radical scavenger), and dolichol (regulator of glycoconjugate metabolism). The pathway was assessed in peptic ulcer and acid peptic disease and its relation to hemispheric dominance studied. The activity of HMG CoA reductase, serum levels of EDLF, magnesium, tryptophan catabolites, and tyrosine catabolites were measured in acid peptic disease, right hemispheric dominant, left hemispheric dominant, and bihemispheric dominant individuals. All the patients with peptic ulcer disease were right-handed/left hemispheric dominant by the dichotic listening test. The pathway was upregulated with increased EDLF synthesis in peptic ulcer disease (PUD). There was increase in tryptophan catabolites and reduction in tyrosine catabolites in these patients. The ubiquinone levels were low and free radical production increased. Dolichol and glycoconjugate levels were increased and lysosomal stability reduced in patients with acid peptic disease (APD). There was increase in cholesterol:phospholipid ratio with decreased glyco­conjugate levels in membranes of patients with PUD. Acid peptic disease represents an elevated EDLF state which can modulate gastric acid secretion and the structure of the gastric mucous barrier. It can also lead to persistence of Helicobacter pylori infection. The biochemical pattern obtained in peptic ulcer disease is similar to those obtained in left-handed/right hemispheric chemically dominant individuals. But all the patients with peptic ulcer disease were right-handed/left hemispheric dominant by the dichotic listen­ing test. Hemispheric chemical dominance has no correlation with handedness or the dichotic listening test. Peptic ulcer disease occurs in right hemispheric chemically dominant individuals and is a reflection of altered brain function.­­­

Monitoring cardiovascular changes during hemodialysis in children.

Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 years) and 11 healthy children were investigated for basic circulatory parameters. Thoracic impedance (Zo) and circulatory parameters were monitored by impedance cardiography (ICG) during HD. Erythrocyte Na+/K+ATP-ase and EDLF were measured before and after HD. Up to the loss of 6% of total body weight, Zo rose linearly with fluid removal, above this no further increase occurred. Heart rate and mean arterial pressure (MAP) were inversely related (r = -0.97); MAP rose in the first and decreased in the second part of HD. Systemic vascular resistance paralleled MAP, whereas stroke volume rapidly decreased, but stabilized in the second part of HD. The ratio of preejection period/ventricular ejection time (PEP/VET) correlated positively with HD duration (r = 0.92), suggesting diminished cardiac filling. Cardiac index (CI) remained stable. EDLF was high in uremia accompanied by depressed Na+/K+ATP-ase (P < 0.05 and P < 0.01, respectively). Following HD Na+/K+ATP-ase normalized. Correlation between Na+/K+ATP-ase activity and MAP was linear (r = 0.85). In conclusion, ICG during HD provides detailed information concerning circulatory adaptation resulting in stable CI, suggesting that the dialysis-induced hypovolemia is compensated by the centralization of the blood volume. Changes of Na+/K+ATP-ase indicate that dialyzable blood pressure-regulating substance(s) inhibit(s) the pump. However, lack of further correlation between Na+/K+ATP-ase, EDLF, and cardiovascular parameters indicates the complexity of the regulatory processes.

Inhibited breathing decreases renal sodium excretion.

This study tested the hypothesis that breathing at the upper end of the normal range of end tidal CO2 decreases renal sodium excretion. Normotensive human subjects learned to self-regulate end tidal CO2 using a respiratory gas monitor and feedback procedure. Urine flow rates were increased by a standardized water drinking regimen. Urinary volume and sodium and potassium excretion were decreased during 30 minutes of inhibited (i.e. high normal end tidal CO2) breathing, compared with levels preceding and after task performance. Blood pressure, but not heart rate, increased during task performance. Plasma volume increase under these conditions is indicated by the observation that urinary excretion of an endogenous digoxin-like factor was increased. The physiological mechanism by which inhibited breathing elicits renal sodium retention remains to be determined. This breathing pattern could mediate the role of behavioral stress in some forms of hypertension.

Endogenous digoxin-like factor in acute myocardial infarction.

The aim of the study was to test the hypotheses that the concentrations of endogenous digoxin-like factor (EDLF) are (i) increased in the initial period after acute myocardial infarction (AMI) and (ii) may contribute to the genesis of ventricular arrhythmias. Consecutive sample study. An 800-bed city teaching hospital, primary hospitalized care centre. Fifty-four consecutive patients of both sexes with a first transmural AMI, 16 male patients with unstable angina pectoris and eight healthy subjects. None. Time-course of the changes of plasma concentrations of EDLF (DELFIA digoxin fluoroimmunoassay) in patients during days 1-14 after uncomplicated AMI and AMI complicated with ventricular fibrillation and congestive heart failure. Plasma concentrations of EDLF in patients on the 1st day after AMI were increased (1.25 +/- 0.26 ng ml-1 digoxin equivalents, P < 0.025) as compared with both healthy controls (0.34 +/- 0.06 ng ml-1) and patients with unstable angina pectoris (0.40 +/- 0.08 ng ml-1). On the 1st day after AMI the plasma levels of EDLF in seven patients with primary ventricular fibrillation were higher (2.54 +/- 0.67 ng ml-1, P < 0.05) than in 47 patients without ventricular fibrillation (1.05 +/- 0.27 ng ml-1). In 14 patients with AMI and congestive heart failure (class III, Killip), plasma concentrations of EDLF were significantly lower (0.32 +/- 0.09 ng ml-1, P < 0.01) than in 40 patients with AMI without congestive heart failure (1.51 +/- 0.32 ng ml-1). Starting from the 2nd day of AMI, plasma EDLF decreased to the level of the control values (0.35 +/- 0.04 ng ml-1) and did not change during a 2-week period of observation. The results show an increase of plasma EDLF during the 1st day after AMI, and that higher plasma EDLF may be associated with the development of ventricular arrhythmias.

The endogenous digoxin-like factor enhances bupivacaine toxicity in rats.

The influence of the immunoreactive endogenous digoxin-like factor (IEDLF) on the systemic toxic effects of bupivacaine was studied in a rodent model. During 5 weeks, IEDLF secretion was promoted in 10 Wistar male rats by allowing them to drink saline 0.5% in place of water. Ten other animals drank desionized water (control). At the time of experimentation, the two groups of rats were mixed to allow blind observation. Anesthesia was induced with barbiturate, and controlled ventilation was started. A blood sample was drawn for IEDLF assessment just before bupivacaine was infused at a constant rate of 2 mg/kg per minute. Data were analyzed for statistical significance using Student's t-test. A p value less than 0.05 was considered significant. Two rats in the saline group died during the induction of anesthesia. An IEDLF activity was found in the eight remaining rats in this group. Threshold doses of bupivacaine's toxic effects (first ventricular arrhythmia, first seizure activity, 25% fall of baseline heart rate, 25% of baseline mean arterial blood pressure, isoelectric electroencephalogram) were significantly lower for the rats with an endogenous digoxin-like activity. There were, however, no significant differences in the lethal dose of bupivacaine. In hyperoxic nonacidotic male rats, IEDLF increases the cardiac and central nervous system toxicity of bupivacaine.

Effect of endogenous digoxin-like factor and digoxin antibody on myocardial Na+, K+-pump activity and ventricular arrhythmias in acute myocardial ischaemia in rats

The aim was to study whether a circulating sodium pump inhibitor (endogenous digoxin-like factor) contributes to the genesis of early ventricular arrhythmias in acute myocardial ischaemia in rats. Effects of digoxin antibody (260 micrograms.kg-1) on the incidence of ventricular arrhythmias, plasma digoxin-like immunoreactivity (DELFIA immunoassay), Na+, K+, and Mg2+ ions, and activity of the ouabain sensitive Na+, K(+)-pump in different regions of myocardium have been studied in propranolol naive and propranolol pretreated rats exposed to acute coronary artery ligation. Adult male Wistar rats were divided into six experimental groups: (1) saline pretreated controls; (2) saline pretreated coronary artery ligated rats; (3) coronary artery ligated rats pretreated with 260 micrograms.kg-1 digoxin antibody; (4) propranolol pretreated controls; (5) propranolol pretreated rats with acute myocardial ischaemia; (6) rats with acute myocardial ischaemia pretreated with both propranolol and digoxin antibody. Acute myocardial ischaemia in saline pretreated rats was associated with a twofold increase of plasma digoxin-like immunoreactivity and ventricular arrhythmias, but did not lead to changes in myocardial Na+, K(+)-pump activity. Pretreatment of coronary artery ligated rats with digoxin antibody reduced the total duration of ventricular tachycardia and ventricular fibrillation during a 15 minute postligation period from 201 (SEM 34) to 46(18) seconds (p < 0.002) but did not alter activity of the myocardial Na+, K(+)-pump. In rats pretreated with propranolol, acute myocardial ischaemia was associated with a twofold inhibition of the Na+, K(+)-pump in left atrial and left ventricular myocardium, and with a 69% increase in plasma K+ concentration. Administration of digoxin antibody to propranolol pretreated coronary artery ligated rats in parallel with the antiarrhythmic effect prevented the increase in plasma K+ concentration and inhibition of Na+, K(+)-pump in the left atrial, but not the left ventricular myocardium. A circulating digoxin-like factor contributes to the pathogenesis of myocardial ischaemia induced ventricular arrhythmias. As propranolol pretreatment of coronary artery ligated rats inhibited the Na, K(+)-pump in myocardium, the inhibitory effect of endogenous digoxin-like factor on Na+, K(+)-ATPase was probably masked in propranolol naive animals by the stimulatory action of catecholamines on Na+, K(+)-ATPase described previously.

Digitalis-like and vasoconstrictor effects of endogenous digoxin-like factor(s) from the venom of Bufo marinus toad.

Digitalis glycoside-like properties of the Bufo marinus toad crude venom and one of its constituents, bufalin, were studied in various assay systems. In concentrations 0.3-30 micrograms/ml crude venom increased the contractility of isolated electrically driven rat atria, constricted rat aortic rings, inhibited ouabain-sensitive Na+,K(+)-ATPase in rat erythrocytes and the Na+,K(+)-pump in rat aorta, and cross-reacted with antidigoxin antibody from the dissociation enhanced lanthanide fluoroimmunoassay (DELFIA). These effects were unaffected by adrenoceptor blockers and the 5-HT antagonist, deseril, but were blocked by antidigoxin antibody. Bufalin (10-30 microM) increased myocardial contractility and inhibited Na+,K(+)-ATPase in rat erythrocytes similarly to crude Bufo marinus venom. In rat aorta bufalin showed weak and delayed vasoconstrictor activity which was antagonized by 2 microM phentolamine, and had a biphasic effect on the Na+,K(+)-pump; 0.5-1.0 microM bufalin stimulated the pump, while higher concentrations inhibited its activity. Although the effects of bufalin were blocked by antidigoxin antibody, bufalin showed very low digoxin-like immunoreactivity in the DELFIA. These observations suggest that, in addition to bufalin, Bufo marinus venom contains at least one more digitalis-like steroid with significant intrinsic vasoconstrictor activity which, unlike bufalin, constricts the blood vessels acting directly via inhibition of the sodium pump in the vascular smooth muscle membrane.

Endogenous digoxin-like factor (EDLF) and lipid peroxidation in acute myocardial ischaemia/reperfusion injury: AY Bagrov, VA Tuyrin, OV Fedorova, NI Roukoyatkina, and YY Tuyrina. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Science, and Dzhanelidze First Aid Research Institute, St.Petersburg, Russian Federation

Endogenous digoxin-like factor (EDLF) and lipid peroxidation in acute myocardial ischaemia/reperfusion injury: AY Bagrov, VA Tuyrin, OV Fedorova, NI Roukoyatkina, and YY Tuyrina. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Science, and Dzhanelidze First Aid Research Institute, St.Petersburg, Russian Federation

Insulin resistance and endogenous digoxin-like factor in obese hypertensive patients with glucose intolerance.

Hypertensive obese subjects with glucose intolerance have hyperinsulinaemia, insulin resistance and intracellular cation imbalance resulting in increased sodium content. The aim of our study was to assess in these patients plasma levels of endogenous digoxin-like factor (EDLF), an inhibitor of the sodium-pump mechanism. We studied 14 hypertensive and 12 normotensive subjects with obesity and glucose intolerance for fasting blood glucose, and plasma insulin, C-peptide and EDLF levels: the two groups were matched for age and BMI and were studied after a 2-week wash-out period from hypotensive drugs. Compared with normotensives, hypertensive subjects had higher plasma insulin levels, a greater immunoreactive insulin/C-peptide ratio, a lower glucose/insulin ratio and higher plasma EDLF levels. Our results confirm that among obese people with glucose intolerance, hypertensives are more hyperinsulinaemic and insulin-resistant than normotensives and indicate that the intracellular cation imbalance in these patients may be attributable, at least in part, to EDLF.

Variation in Apparent Serum Digitalis-like Factor Levels With Different Digoxin Antibodies: The "Immunochemical Fingerprint"

Increased levels of a circulating digoxin-like factor (DLF) occur in a number of physiologic states in which sodium homeostasis is altered, and may contribute to the pathogenesis of hypertension. We exploited the different affinities for DLF of seven antisera directed at digoxin to develop an immunochemical profile, and then employed this index to address two questions: does the same DLF species exist in several conditions associated with increased DLF levels, including pregnancy, renal failure, hepatic failure, and neonatal cord blood? Will this approach prove useful in assessing candidates proposed to be DLF? An identical profile was identified in serum from pregnant women and patients with renal or hepatic failure, and a highly significant correlation existed between DLF levels measured with antisera of high and intermediate affinity in 42 subjects with increased levels (r = 0.93; P less than .001). In patients with renal failure, when endogenous DLF levels were too low to assess the profile, concentration of the serum resulted in measurable DLF levels that had an identical profile. The profile was somewhat altered in umbilical cord blood, perhaps reflecting an influence of increased steroid hormone levels. Among agents suggested as candidates for DLF, neither lysophosphatidylcholine nor ouabain showed a profile resembling DLF. Progesterone, 17-OH-progesterone, and bufalin, on the other hand, did show substantial similarity, perhaps providing a clue to the structure of DLF. The normal plasma levels of progesterone and 17-OH-progesterone are 100- to 1000-fold too low to be candidates for DLF and bufalin was sufficiently dissimilar not to be a candidate. DLF in at least three different patient populations probably represents identical chemical species.(ABSTRACT TRUNCATED AT 250 WORDS)

Digoxin enhances bupivacaine toxicity in rats.

The influence of digoxin on the systemic toxic effects of bupivacaine was studied in a rodent animal model. The experiment was undertaken with consideration to clinical situations such as pregnancy that are associated with the secretion of an endogenous digoxin-like factor. Twenty Wistar male rats, under barbiturate anesthesia and controlled ventilation, received either 5 micrograms/kg intravenous digoxin (n = 10) or saline (n = 10), blinded to the observer. Digoxin serum concentration was 1.8 +/- 0.24 ng/ml in the study group. Thirty minutes after digoxin or saline was administered, bupivacaine was infused at a constant rate of 2mg/kg/minute. The threshold doses of bupivacaine toxic effects (first ventricular arrhythmia, 25% fall of baseline heart rate, 25% fall of baseline mean arterial blood pressure, first seizure activity, isoelectric electroencephalogram, and asystole) were significantly lower in the digoxin group, as were the lethal bupivacaine serum concentrations. Digoxin, in hyperoxic nonacidotic rats, increases the cardiac and central nervous system toxicity of bupivacaine. Based on the known electrophysiologic actions of these two drugs, a synergistic toxic interaction is demonstrated.

Antiarrhythmic effect of antibodies to digoxin in experimental myocardial infarction (the arrhythmogenic action of endogenous digoxinlike factor)

Antiarrhythmic effect of antibodies to digoxin in experimental myocardial infarction (the arrhythmogenic action of endogenous digoxinlike factor)

Endogenous digoxin-like factor (EDLF) in acute myocardial infarction (AMI): Alexey Ya.Bagrov, Olga V.Fedorova, Marina N.Maslova, Natalia I. Roukoyatkina, Maria V. Ukhanova, and Eugenii P.Zhabko. I.I.Dzhanelidze First Aid Research Institute, and I.M.Sechenov Institute of Evolutionary Physiology and Biochemistry Acad. Sci. USSR, Leningrad, USSR

Endogenous digoxin-like factor (EDLF) in acute myocardial infarction (AMI): Alexey Ya.Bagrov, Olga V.Fedorova, Marina N.Maslova, Natalia I. Roukoyatkina, Maria V. Ukhanova, and Eugenii P.Zhabko. I.I.Dzhanelidze First Aid Research Institute, and I.M.Sechenov Institute of Evolutionary Physiology and Biochemistry Acad. Sci. USSR, Leningrad, USSR

Endogenous Digoxin-Like Factor in Neonates: Effect of Age and Relation to Serum Bilirubin Levels

Endogenous digoxin-like immunoreactive factor(s) (DLIF) have been found in serum and urine of newborn infants, including those born prematurely. We assessed the effect of age on serum levels of DLIF in 73 samples obtained from 66 healthy full term newborn infants at birth and during the first two months of life. DLIF concentrations were highest at birth and fell progressively with age. In cord blood, DLIF levels were 0.73 +/- 0.35 ng/ml (mean +/- SD). DLIF concentrations were 0.45 +/- 0.11 ng/ml on day 1, 0.26 +/- 0.08 ng/ml on day 3, 0.19 +/- 0.07 ng/ml on day 5, 0.17 +/- 0.09 ng/ml on day 11, 0.11 +/- 0.02 ng/ml on days 15-30, and not detectable after 45 days of life. We also studied the relation between serum levels of DLIF and bilirubin in 23 jaundiced newborns between 3-5 days of life. We found a highly significant positive correlation between serum bilirubin concentrations and DLIF. These findings support the assumption that DLIF plays a role in impeding bilirubin excretion in the neonatal period, perhaps by inhibiting the activity of (Na-K)ATPase.

Endogenous digoxin-like factor raises blood pressure and protects against digitalis toxicity

Digoxin-like immunoreactive factor (DLIF) is an endogenous natriuretic material which causes diuresis and natriuresis after salt or fluid loading and which may play a pathogenetic role in various hypertensive states. In order to study the cardiovascular effects of DLIF, we administered partially purified material (500 ng/kg) iv to normal rats. DLIF administration caused a significant rise in blood pressure, induced a brisk diuresis, and slowed the heart rate. In addition, DLIF protected against digitalis toxicity. While iv digoxin, 1 mg/kg, uniformly produced lethal arrhythmias, administration of DLIF 15 min prior to digoxin infusion consistently protected against arrhythmias. These findings support the theory that DLIF may play a role in hypertension. In addition, DLIF may compete with digoxin for cardiac receptors.

Functional antagonism by monoclonal antibody to digoxin in the guinea-pig atria

A monoclonal antibody with a high affinity for digoxin (K a = 1.14 × 10 9 M) was produced by somatic cell fusion. This antibody, designated 35 6.1 , displayed little or no cross reactivity with other steroids. In the guinea-pig atria, 35 6.1 antagonized functionally the positive inotropic effect of digoxin but did not alter that of isoproterenol. Our results suggest that this monoclonal antibody may represent a useful probe for studying the physiological role of the putative endogenous digoxin-like factor in various pathophysiological conditions.

The importance of endogenous digoxin-like factors in rats with various forms of experimental hypertension.

The acute administration of anti-digoxin serum (ADS) caused a pronounced long-lasting blood pressure decrease in young DOCA-salt hypertensive rats. The decrease of blood pressure was only moderate in 1K-1C Goldblatt rats while there was no change of blood pressure after the ADS injection in spontaneously hypertensive rats. However, the blockade of endogenous digoxin-like factors lowered blood pressure only in those hypertensive rats which were treated with DOCA-saline from youth but not in animals treated in the same manner only in adulthood. The age period at which salt intake was increased, could be responsible for the susceptibility of animals to salt- and volume-dependent forms of experimental hypertension as well as for the participation of slow acting humoral pressor agents in the induction and/or maintenance of elevated blood pressure. It is evident that endogenous digoxin-like factor(s) participate in a greater response of young rats to the hypertensive stimuli.

Increased circulating levels of an endogenous digoxin-like factor in hypertensive monkeys.

An endogenous, immunoreactive digoxin-like factor (endoxin) was measured in the plasma of nonhuman primates with hypertension. Both normotensive and hypertensive rhesus monkeys had levels of endoxin that significantly correlated with their systolic or diastolic blood pressure. Vervet monkeys with experimentally produced chronic Goldblatt hypertension had significantly elevated endoxin, but not plasma renin. These data suggest that increased plasma endoxin may be a contributing factor in the development of hypertension.