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Endogenous digitalis-like factor (EDLF), an inhibitor of membrane Na+/K(+)-ATPase, is discussed to be involved in the pathogenesis of cirrhogenic portal hypertension, ascites formation and development of functional hepatorenal failure. Therefore, we investigated the serum content of this mediator in patients with liver cirrhosis Child-Pugh stage A, B, and C (n = 27) by means of enzyme immunoassay with a specific digoxin antibody. Furthermore, a correlation analysis was performed in order to find out correlations between signs of cell injury, cholestasis, synthetic cell function, ascites formation, and hepatorenal failure. Our results demonstrate that EDLF is significantly elevated in Child C cirrhosis (0.61 +/- 0.15 ng/ml) in comparison to Child A cirrhosis (0.013 +/- 0.2 ng/ml) and is also higher than in Child B cirrhosis (0.23 +/- 0.25 ng/ml). In patients without ascites EDLF (0.056 +/- 0.19 ng/ml) differs significantly from that of patients with non-complicated ascites (0.156 +/- 0.176 ng/ml) and from that of patients with therapy refractory ascites (0.66 +/- 0.17 ng/ml) or hepatorenal failure (1.56 ng/ml). There are no correlations between EDLF and renal function. Significant correlations were demonstrated for cholestasis (serum bilirubin), synthesis function (serum protein, Quick's value, cholinesterase, fibrinogen, albumin), and the degree of portasystemic encephalopathy (number connection test). We conclude that EDLF may act as a mediator in the process of progressive portal hypertension and its complications due to cirrhosis. This process of progression is caused by the inhibition of Na+/K(+)-ATPase, vasoconstriction, and endothelin secretion.

The existence of an endogenous natriuretic hormone and ouabain-like factors (OLF) has been postulated for many years. This postulate was based on our original observation that a small M.W. fraction in the serum after acute expansion of the extracellular fluid volume (ECFV) not only exhibited natriuretic activity but also inhibited the Na-K-ATPase enzyme in vitro similar to ouabain. Since then, numerous studies confirmed the presence of OLFs in serum, urine, cerebrospinal fluid, and various organs including the heart and hypothalamus. Some of these OLFs are well-known endogenous compounds, such as free unsaturated fatty acids, which inhibit in vitro transmembranous sodium transport, Na-K-ATPase and 3H-ouabain binding to its membrane receptor or cross-react with digoxin antibodies. Chemically yet undefined OLFs of potentially hypothalamic origin were detected in various models of experimental and clinical hypertension and are suggested to play a pathophysiological role especially in salt- and volume-dependent forms of hypertension. Our results show that OLFs isolated from the urine of salt-loaded healthy subjects strongly enhance basal and vasopressin-stimulated release of calcium in vascular smooth muscle cells and platelets similar to the effects we had observed with endothelin. This urine fraction also exhibits natriuretic activity which increases in parallel with sodium intake. Further chromatographic separation and amino acid analysis confirmed the peptidic nature (M.W. less than 1000) of the natriuretic factor(s). However, the two biological activities, namely natriuretic and ouabain-like activities, reside in distinct and chemically different compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

The estimation of serum digoxin is a usual method in intensive care. In a case report the detection of digoxin-like-immunoreactive-factor (DLIF) is shown, which gives false high levels. DLIF is observed in renal damage, high cardiac activity, pregnancy and newborn.

A digoxin-like immunoreactivity (DLIS) was measured by two routinely used clinical digoxin-immunoassays (radio- and enzymeimmunoassay) in cord blood of 255 newborns, in sera of their mothers at birth and in sera of 211 newborns during the first two postpartal weeks. The highest DLIS levels were found in serum of neonates at the first day of life (median: 0.23 ng/ml, 25% and 75% percentile: 0.19 and 0.28 ng/ml) and in cord blood (median: 0.21 ng/ml, 25% and 75% percentile: 0.19 and 0.24 ng/ml); maternal serum was shown to have three times less DLIS (median: 0.08 ng/ml, 25% and 75% percentile: 0.05 and 0.10 ng/ml). There was no significant correlation between DLIS concentrations in serum of newborns, cord blood or pregnants. The DLIS serum levels of preterms with birthweight less than 2500 g and gestational age less than 37 weeks were significantly lower than those of normal neonates at term (p less than 0.01); concomitantly the lowest DLIS levels were found in maternal serum of preterms (p less than 0.01). These observations strongly suggest rather a DLIS origin in the newborn than in the mother. During the first two postpartal weeks the DLIS concentration of a vast majority of the 211 newborns (91%) decreased continuously to one half of the starting value. Within the second postpartal week preterms were found to have a significantly delayed decrease in the DLIS serum levels (p less than 0.01). Small for date newborns showed no difference in their postpartal DLIS time course compared to normal neonates.(ABSTRACT TRUNCATED AT 250 WORDS)

In the renal compensatory adaptation after the definition and the description of the fundamental phenomena of the functional compensation as well as of the structural adaptation is reported on mediator concepts and on modulations of the renal adaptation processes. Issuing from the central position of the sodium balance a mediator concept on natriuretic hormones (Auriculin and Endoxin) is developed which is supplemented by the renotropin mediator concept. The authors deal with the modulation of the renal compensatory adaptation (e.g. influences of age diet and so on). The pharmacotherapeutic modulation of the renal compensatory adaptation is discussed with regard to the stimulation of the tubulosecretory transport of foreign substances with para-amino hippuric acid as principal substance (including own investigations with cyclopenthiazide [Benesal].

A dualistic function for the natriuretic ATP.inhibiting factor is formulated on the basis of a phenomenon like compensatory renal adaption of residual nephrons: 1. Support of the tubular sodium excretion to the maintenance of homoeostasis of the organism. 2. Inhibition of the forced up vasodilation of the afferent glomerular vessel. It should suggested that the renal vasoconstrictive effect is a part of a protective system for residual nephrons against the pathogenic hyperfiltration and hyperperfusion.

An algorithm worked on basis of quantitative relations between molecular-biologically defined effects and molecular-physical properties (see part 1) allows the effect estimation of concepted cardenolides before their synthesis. The empirical use of the developed equations for the estimation of molecular-biologically defined effect of compounds produces usable results and justifies therefore the proposed method, as well as it's shown by the experimental proof of estimated values of some cardenolides . An enlargement of the use of the algorithm for effect estimation seems to be successful.

Human beings and higher animals contain compounds which interact with the Na+/K+-ATPase of the heart muscle and other organs like the cardiac glycosides, and bind to cardiac glycoside-specific antibodies [endogenous digitalis-like substance(s), EDLS]. EDLS cause increased natriuresis. The level of EDLS of the blood is raised under physiological stress situations (e.g., pregnancy and delivery and at certain pathophysiological conditions (e.g., hypertony). The EDLS are low molecular compounds. As yet their chemical structure is unknown.

Intestinal absorption of 15 cardenolides has been examined in cats. The 3H-labelled substances were injected intraluminally into ligated duodenal loops of anaesthetized animals. 3H-Concentrations were followed in the portal circulation and in the bile. 1 h after drug administration the duodenal sac was removed, and the residual in the lumen then was washed out and assayed radiochemically. The decrease of radioactivity during 1 h was calculated as extent of absorption (QR). Cardenolide absorption was compared with the corresponding in vitro parameters of lipophilicity like octanol/water partition coefficients and Rm values from reversed phase thin-layer chromatography. The Spearman rank sum correlation test revealed coefficients of 0.95 to 0.97. The result lends support to the use of the easily available Rm values as a good tool to predict intestinal absorption of various cardenolides.

Partition coefficients (P) of 48 cardenolides were determined in octanol/water. Furthermore Rm-values of most of these substances were measured in different thin-layer chromatography systems (TLC) and related to P. Regression analysis revealed that the best linear fit of the data was obtained when Rm-values from reversed-phase TLC on octanol impregnated silica-gel layer as stationary phase and methanol/water as mobile phase were correlated with log P (r = 0.91). A better correlation between these two sets of data was obtained by restricting the calculations to groups of cardenolides with similar structural features (r = 0.96-0.98). The present results are showing that Rm-values from reversed-phase TLC--a rapid and reproducible method with many advantages over the tedious measurement of P--can be used to predict P.

By equilibrium dialysis the binding of 19 cardenolides and cardenolide conjugates to human plasma proteins has been measured. The binding constants were compared with octanol-water partition coefficients described previously. No correlation was found between the two properties. Glycosides and conjugates of a certain genine show the same extent of protein binding, even if some of the derivatives differ in their physicochemical properties more than by three log units. It is concluded that cardenolide protein binding depends solely on hydrophobic property of the genine involved.

Knowing the modell developed by Repke and co-workers for the cardenolide-receptor-interaction the aim of this study was to find quantitative relations between molecular physical properties of cardenolides and their molecular-biologically defined effect, which are fundamentally useful to estimate the effect of still nonsynthesized cardenolide derivatives. The statistically significant relations (alpha = 0.05) between molecular physical parameters, which are derived from the dipole moment vector, and the molecular-biologically defined effect was found by means of regression analysis.

Cardenolide glucuronides are synthesized in the following way: firstly cardenolide glucosides are prepared by the reaction with acetobromglucose; secondly the hydroxymethyl group of the glucose moiety is oxydized in presence of a platinum catalyst to the carboxyl group of the final glucuronic acid. Glucuronides of the following cardenolides are prepared and described: digoxin, digoxigenin, digitoxin, digitoxigenin-monodigitoxoside, digitoxigenin, and 3-epi-digitoxigenin. Sulphates of digoxigenin, digitoxigenin, and 3-epi-digitoxigenin are prepared by direct reaction of these cardenolides with chlorosulphonic acid in pyridine. The assumed structure of some conjugates has been confirmed by n.m.r. spectroscopy. A high water solubility (6.7-65.1 g/l), a minute chloroform solubility (0.0002-0.0005 g/l), and a low octanol/polar nature of these compounds. Inotropic or toxic cardiac activities of the conjugates are examined on isolated guinea pig papillary muscles and by the Hatcher method on cats. Conjugates with at least one digitoxose show cardioactivities comparable to digoxin or digitoxin. In contrast to that the conjugated genins indicate decreased activities which are at least one-tenth of the potency of the unconjugated glycosides.