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Biomedical subjects

W Krawietz

Publications and source records attributed to W Krawietz.

At least 55 records · Page 3Linked to original sources
PubMed1978

Effect of some Pteridine compounds on the Na+ + K+)-ATPase and on the cardiac glycoside receptor of human heart).

Pteridine compounds are known to block Na+-reabsorption and K+-secretion in epithelial cells (salivary duct of the rat), which actively transport Na+ and K+ against an electrochemical gradient. Furthermore, there have been reports on antagonistic effects of these substances in digitalis induced arrhythmias. Therefore the actions of triamterene (Jatropur, Dyrenium), the sulfuric acid ester and the methylether of p-hydroxytriamterene (OH-triamterene) and OH-triamterene on specific [3H] g-strophanthin (ouabain) binding and Na+ + K+)-ATPase activity of isolated human cardiac cell membranes were investigated. Triamterene, the sulfuric acid ester and the methylether of OH-triamterene inhibit (Na+ + K+)-ATPase activity only at very high concentrations (10(-5)--10(-4) M). OH-Triamterene does not inhibit this enzyme at concentrations lower than 10(-3) M. The specific binding of [3H] g-strophanthin to human cardiac cell membranes is inhibited half maximally at relatively high concentrations, too (10(-5)--10(-4) M). These results are rather indicative of unspecific effects due to membrane sites of action other than the (Na+ + K+)-ATPase or the cardiac glycoside receptor.

Adenosine Triphosphatases↗
PubMed1977

[Cardiac effects of antikaliuretic diuretics-clinical and biochemical investigation (author's transl)].

Recently direct myocardial effects of antikaliuretic diuretics with respect to contractility parameters and prevention of digitalis-induced arrhythmias were published. In order to test the value of these reports we measured the effect of potassium-canrenoate and triamterene on cardiac output and on digitalis-induced arrhythmias in patients during diagnostic and the therapeutic flow directed right heart catheterization (Swan-Ganz) in our intensive care unit. In addition the influence of these drugs on (Na+ + K+)-ATPase and on (3H)g-strophanthin binding to human cardiac cell membranes was investigated to gain information on the mechanism of their action. Triamterene (100-200 mg p.o.) was without any effect on cardiac output, the same was found true for potassium-canrenoate given in a single dose (200-1000 mg intravenously). However, when applied in two doses (200 mg i.v. and 60 min later 400 mg i.v.), potassium-canrenoate increased cardiac output by 11 percent (p less than 0.05). Only in 2 out of 14 patients potassium-canrenoate (200-400 mg i.v.) suppressed digitalis-induced ventricular ectopic beats. Canrenone, the active metabolite of potassium-canrenoate displaces [(3H)]g-strophanthin from its binding sites in human cardiac cell membranes and inhibits (Na+ + K+)-ATPase activity. These in vitro effects were measured at the same concentrations as found in vivo after "therapeutical" doses. The effects of triamterene in this respect were found only in extremely high concentrations. Our results imply that canrenone has cardiac glycoside-like effects in human cardiac cell membranes.

Adenosine Triphosphatases↗
PubMed1976

[Significance of serum digoxin concentration and its influencing factors].

In recent years it has become possible by means of a radioimmunoassay to measure Digoxin concentration in the serum of digitalized patients. With this method it could be shown that the resorption of Digoxin is decreased by partial resection of the samll intestines, by malabsorption syndromes, after ingestion of Neomycin, Colestyramine and antacids. In renal insufficiency, however, the elimination half-life period of Digoxin is increased conspiciously (from about 35 hours up to about 120 hours). This results in a raised serum concentration of cardiac glycosides unless the dosage is decreased considerably. The incidence of Digitalis intoxication in Digitalis treated patients has been reported to rank as high as 20%. There is, however, no strict correlation between the serum glycoside level and the clinical symptoms, because the glykoside concentration in the serum does not represent the pharmacologically active concentration at the receptor. Experimental investigations of cardiac glycoside binding to the receptor for cardiac glycosides in human heart cell membranes revealed, that receptor bound Digoxin for instance is diminished in serious renal insufficiency and it depends on the serum concentration of potassium, calcium and magnesium. In hypoxia, after myocardial infarction and in myxedema the sensitivity for cardiac glycosides is increased. The opposite is true in hyperthyreoidism, fever and in children. All of these factors have to be kept in mind and paid attention to in the clinical evaluation of the measured Digoxin concentration in the serum.

Cardiac Complexes, Premature↗
PubMed1976

[Case report of a primary pericollagen amyloidosis (author's transl)].

The authors report about a female patient, 59 years old, who was suffering from a stenosis of the cardia. A malignant process was suspected and an operative treatment was planed. During the preoperative internal examinations a low voltage in the ECG was found so that an amyloidosis was suspected. This was proved by biopsy of the mucosa of the rectum. A chronic suppurative disease could not be found, it was then assumed that the patient is suffering from a "primary pericollagen amyloidosis". Because a splitting of the stenosis through the esophagoscope the biopsy showed no malignancy, but congo-red positive material around collagen tissue. This seldom disease, the differential-diagnosis and the possibilities of treatment are discussed. Under symptomatic therapy the patient is doing well 2 years since.

Amyloidosis↗
PubMed1976

Beta-adrenergic receptors in guinea-pig myocardial tissue.

Stereospecific binding sites for (-) [3H]-alprenolol, a beta-adrenergic antagonist, have been identified in guinea-pig myocardial broken cell preparations. The concentration of the sites was 0.3 pmoles per mg of protein and the dissociation constant (at 37 degrees C) 10(-8) M. A close correlation between the ability of various beta-adrenergic antagonists to compete with tracer alprenolol binding and to block the response of isoprenaline-stimulated myocardial adenylate cyclase has been found. Low affinity sites for the labelled beta-adrenergic antagonist in contrast to stereospecific sites are heat stable and do not discriminate between the (-) and the (+) forms of the beta-adrenergic antagonists. Adenylate cyclase in guinea-pig myocardial tissue is poorly stimulated by isoprenaline or 5'-guanylylimidodiphosphate. This is attributed to a high basal activity which could be lowered by a preincubation at 37 degrees C.

Adenylyl Cyclases↗
PubMed1976

On the action of triamterene on isolated cell membranes.

Recently there have been recurring reports on extrarenal and expecially on antiarrhythmic effects of triamterene, the latter ones being observed particularly in cases of digitalis intoxication. Considering the digitalis-antagonistic effects, which are also observed in the course of experimental investigations, it was assumed that triamterene, a potassium-saving diuretic, displaces cardiac glycosides from their binding sites in cardiac membranes. The binding of [3H]-g-strophanthin ([3H]-ouabain) and the activity of the (Na+ + K+)-ATPase in the presence of different concentrations of triamterene have been studied with isolated cardiac cell membranes (human; bovine) and human erythrocyte membranes. Inhibition of the binding of the cardiac glycoside and the enzyme activity was only observed for very high concentrations of the active component. These observations are indicative of non-specific effects. Triamterene applied in the presence of different concentrations of strophanthin (10(-9)--5 X 10(-7) M) did not display protective effects on the (Na+ + K+)-ATPase activity. In experiments aimed at chromatographic separations, it could be shown that [3H]-triamterene binds to membrane proteins different from those binding [3H]-g-strophanthin, the latter having been shown to be present in the (Na+ + K+)-ATPase containing fraction. From the results of these experiments it may be concluded that there is no interaction between triamterene and strophanthin on the membrane bound receptor for the cardiac glycoside. [3H]-Triamterene shows concentration dependent binding to cell membranes. This binding is affected to different degrees by Mg++, K+, Na+ and Ca++. The binding sites show low affinity but high binding capacity for triamterene. The significance of this fact remains to be established.

Adenosine Triphosphatases↗
PubMedDate not supplied

Stimulation of human cardiac adenylate cyclase by vanadate.

Experiments have been carried out to characterize the influence of the positive inotropic trace element vanadium (used as Na3VO4) on beta-adrenergic receptor coupled adenylate cyclase activity from human myocardium. Na3VO4 (10(4)M) stimulates basal activity as well as isoprenaline (10 microM)- and Mg2+ (20 mM) activated enzyme activity 1.5-2.4-fold. In contrast, adenylate cyclase activity in the presence of maximally activating concentrations of Gpp(NH)p (10 microM) cannot be further increased by Na3VO4. The results confirm the assumption (5) that vanadate stimulates adenylate cyclase by interacting with the nucleotide-binding site of this enzyme.

Adenylyl Cyclases↗