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At least 19 recordsLinked to original sources
PubMed1986

Naturally occurring cardiac glycosides.

Cardiac glycoside poisoning from the ingestion of plants, particularly of oleanders, occurs with reasonable frequency in tropical and subtropical areas. We have assessed a variety of plant specimens for their cardiac glycoside content by means of radioimmunoassays with antibodies that differ in their specificity for cardiac glycosides. Significant amounts of immunoreactive cardiac glycoside were found to be present in the ornamental shrubs: yellow oleander (Thevetia peruviana); oleander (Nerium oleander); wintersweet (Carissa spectabilis); bushman's poison (Carissa acokanthera); sea-mango (Cerbera manghas); and frangipani (Plumeria rubra); and in the milkweeds: redheaded cotton-bush (Asclepias curassavica); balloon cotton (Asclepias fruiticosa); king's crown (Calotropis procera); and rubber vine (Cryptostegia grandifolia). The venom gland of the cane toad (Bufo marinus) also contained large quantities of cardiac glycosides. The competitive immunoassay method permits the rapid screening of specimens that are suspected to contain cardiac glycosides. Awareness of the existence of these plant and animal toxins and their dangers allows them to be avoided and poisoning prevented. The method is also useful for the confirmation of the presence of cardiac glycosides in serum in cases of poisoning.

Amphibian Venoms↗
PubMedDate not supplied

A comparative dose-effect study with cardiac glycosides assessing cardiac and extracardiac responses in normal subjects.

We tested the hypothesis that differences exist in the pharmacodynamic pattern of different cardiac glycosides. We conducted a randomized, placebo-controlled study in normal volunteers and evaluated the effects of weekly increased oral dosing of digoxin (n = 10; from 0.25 to 1.0 mg/day), meproscillarin (n = 10; from 0.5 to 2.0 mg/day), and placebo (n = 5). To determine the glycoside effects, corrected electromechanical systole (QS2c) was used to measure inotropy and the PQ interval to test dromotropy. Red-green discrimination and critical flicker fusion (CFF) assessed visual functions. Subjective complaints were collected using rating lists. Both glycosides dose dependently shortened QS2c and prolonged PQ interval. PQ prolongations over +20 ms occurred in seven of 10 digoxin subjects, in two of 10 meproscillarin, and in one of five placebo. Equi-inotropic response, identified at 12 ms mean QS2c shortening, revealed the relative potency of digoxin to be 2.4 times higher than meproscillarin; this ratio increased to sevenfold for equi-effective negative dromotropic effects at 12 ms mean PQ prolongation. Each drug was associated with a dominant subjective complaint: digoxin with anergy and meproscillarin with diarrhea. Red-green discrimination was better under meproscillarin and CFF was depressed by digoxin. The results indicate that pharmacodynamic differences exist between cardiac glycosides. A differential use of various glycosides should be considered and tested clinically.

Adult↗
PubMed1981

[Rhythm and conduction disorders caused by cardiac glycosides].

Cardiac glucosides could cause almost all kinds of rhythm and conduction disorders. In 648 patients treated with cardiac glucosides, rhythm and conduction disorders were recorded in 124 patients--19.1 per cent (58 males and 60 females), aged from 17 to 76. Ventricular extrasystoles rank first according to incidence--47 per cent; ventricular bigeminy--24.3 per cent; AV block stage I--23.4 per cent, etc. From all the 124 patients registered with intoxications induced by cardiac glucosides--one patient died, very likely due to ventricular fibrillation--0.89 per cent lethality. Toxic symptoms with initial saturation with digitalis preparation is most frequently observed in patients with grave myocardial lesions as well as rheumatic activity, accompanied by cardiac decompensation and a parallel administration of potent diuretic treatment that favours hypopotassemia and glucoside intoxication.

Adolescent↗
PubMed1979

A specific cardiac glycoside for cardiac failure and another for atrial fibrillation?

Ouabain produces a greater degree of prolongation of the P-R interval than digitoxin in rats when dosages which produce similar inotropic responses are used. When digitoxin is administered after pretreatment with propranolol, it produces prolongation of the P-R interval comparable to that produced by ouabain. Indications in the literature that these findings may apply to human beings suggest that in some situations atrial fibrillation may be better controlled with a hydrophilic digitalis preparation (e.g. ouabain), whereas cardiac failure with a tendency to atrioventricular block may be better controlled with a lipophilic preparation (e.g. digitoxin).

Animals↗
PubMed1986

Cardiac glycosides. 7. Sugar stereochemistry and cardiac glycoside activity.

Digitoxigenin alpha-L-, beta-L-, alpha-D-, and beta-D-glucosides; alpha-L-, beta-L-, alpha-D-, and beta-D-mannosides; and alpha-L- and beta-L-rhamnosides were stereoselectively synthesized from the corresponding sugar tetrabenzyl trichloroacetimidates. The Na+,K+-ATPase receptor inhibitory activities of these glycosides (as a measure of receptor binding) were compared with those of digitoxigenin, digitoxigenin 6'-hydroxy-beta-D-digitoxoside, digitoxigenin beta-D-galactoside, and digitoxigenin beta-D-digitoxoside. The observed activities reveal that a given sugar substituent may have a role in binding of some glycoside stereoisomers, but not others. With alpha-L- and possibly beta-L-rhamnosides, the 5'-CH3 and 4'-OH appear to have a predominant role in binding to the Na+,K+-ATPase receptor. Addition of a 6'-OH to form the corresponding mannosides dramatically disrupts the effect of both the 5'-CH3 and 4'-OH in prompting receptor binding of the alpha-L isomer. However, with the beta-L isomer, some influence of 4'-OH, 3'-OH, and 2'-OH binding remains. With beta-D-glycosides, binding via the "5'-CH3 site" appears to be of little importance and addition of a 6'-OH diminishes activity only slightly. With these beta-D-glycosides, an equatorial 4'-OH, axial 3'-OH, and equatorial 2'-OH groups appear to contribute to binding.

Cardiac Glycosides↗
PubMed1993

Kinetic analysis of ouabain binding to native and mutated forms of Na,K-ATPase and identification of a new region involved in cardiac glycoside interactions.

Cardiac glycosides inhibit the Na,K-ATPase by binding to the catalytic alpha subunit of the enzyme. Site-directed mutagenesis of the H1-H2 domain has demonstrated the importance of this region in determining cardiac glycoside affinity. In this study, random mutagenesis was used to identify an amino acid, arginine 880, in the COOH-terminal portion of the alpha subunit which influences the sensitivity of the enzyme to ouabain. This residue is predicted to reside in the H7-H8 extracellular loop. Conversion of arginine 880 to a proline causes a 10-fold increase in the dissociation rate constant and a 2-fold increase in the association rate constant for [3H]ouabain binding. This results in an enzyme with a KD for ouabain 5-fold higher than the wild-type sheep alpha 1 isoform. These data are compatible with arginine 880 comprising a portion of the ouabain binding site. Furthermore, if arginine 880 is at the physical binding site, then this finding lends support to models that place this amino acid extracellularly since cardiac glycosides interact with the extracellular surface of the Na,K-ATPase. The ouabain binding characteristics of substitution R880P were compared with those of several different Na,K-ATPases, each of which contains a single amino acid substitution in the H1-H2 region of the alpha subunit. The substituted enzymes, C104A, Y108A, E116Q, P118K, and Y124F, vary considerably in their rates of dissociation (1-4-fold increase in the dissociation rate constant). In addition, the rate of association of [3H]ouabain binding to substitution P118K is 2-fold slower than that of the wild-type enzyme. These results suggest that the H1-H2 domain may participate directly in ouabain binding as well as be involved in conformational changes, both of which could affect the sensitivity of the enzyme to ouabain.

3T3 Cells↗