Role of catecholamines in the central mechanism of emetic response induced by peruvoside and ouabain in cats.
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1 Peruvoside, (a glycoside obtained from the plant, Thevetia neriifolia Juss) and ouabain produce emesis in cats. Vomiting is not produced by these drugs in animals pretreated with catecholamine depleting drugs like reserpine, tetrabenazine or syrosingopine. Chloropromazine hydrochloride, mepyramine maleate, or BOL-148 administered intravenously or intracerebro-ventricularly do not afford protection.2 Phenoxybenzamine produces partial protection against peruvoside-induced emesis.3 Haloperidol (1 mg/kg i.v.) prevents vomiting induced by peruvoside or ouabain. Intracerebroventricularly administered haloperidol is ineffective.4 Cats pretreated with SKF-525-A, are not protected by haloperidol. Animals pretreated with phenobarbitone in a dose of 25 mg/kg for a week were protected by haloperidol, 250 mug/kg i.e. one quarter of the effective antiemetic dose in normal cats.5 It is postulated that catecholamines are involved in the mechanism of vomiting induced by cardiac gycosides. Further, a metabolite of haloperidol seems to be responsible for its effective antiemetic action. (+info)
Systolic time intervals in constrictive pericarditis. A study before and after digitalis.
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Systolic time intervals were studied in 9 patients with documented constrictive pericarditis before and 15 to 20 minutes after intravenous administration of peruvoside (a quick acting digitalis-like glycoside) to determine underlying myocardial dysfunction. Data were compared with those of similarly studied normal subjects and patients with known myocardial dysfunction. Left ventricular ejection time index (LVETI) decreased in normal subjects (P less than 0.01) and in most patients with constrictive pericarditis, and increased marginally in those with myocardial dysfunction (NS) after peruvoside administration. Pre-ejection period index (PEPI) shortened significantly (P less than 0.01) after peruvoside in normal subjects and in patients with myocardial failure, but not in constrictive pericarditis. Likewise the predicted ejection fraction was insignificantly altered in constrictive pericarditis but significantly so (P less than 0.01) in myocardial failure and normal subjects. The response of one patient with constrictive pericarditis to parenteral peruvoside administration was similar to that seen in patients with myocardial failure. This patient had a delayed recovery after pericardiectomy. PEPI/LVETI ratio and ejection fraction were also abnormal in other patients with constrictive pericarditis when compared to normal subjects. Such abnormalities and the unusual response of some patients to administration of peruvoside may reflect underlying myocardial dysfunction in patients with constrictive pericarditis. However, it is possible that the rigid pericardium also contributes to these abnormalities to a varying extent. Systolic time indices and their response to digitalis appear to be a useful, atraumatic method for detecting underlying myocardial dysfunction in patients with constrictive pericarditis. (+info)
Cardiotonic steroids: correlation of sodium-potassium adenosine triphosphate inhibition and ion transport in vitro with inotropic activity and toxicity in dogs.
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1. A new series of cardiotonics based on five steroid nuclei has been evaluated for inhibition of Na-+/K-+-ATPase and Rb uptake by red blood cells, and for inotropic activity and toxicity in dogs. Structure-activity relationships are discussed. 2. The in vitro tests can be used satisfactorily to predict inotropic activity, but not toxicity or therapeutic ratio. 3. Although compounds with greatly improved therapeutic ratios relative to ouabain and tolusin have been obtained, they proved to be strongly emetic in the conscious dog. (+info)
Novel digitalis-like factor, marinobufotoxin, isolated from cultured Y-1 cells, and its hypertensive effect in rats.
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Marinobufagenin and telecinobufagin have been identified as digitalis-like factors in mammals. In toads, marinobufagenin-related compounds, such as marinobufotoxin (MBT), have been isolated in some tissues but not in mammals, and its biological action has not been elucidated. Herein, we aimed to explore the possible production and/or secretion of MBT and the biological action in rats. First, the MBT in culture supernatant of the adrenocortical-originated cell line Y-1 was analyzed by high-performance liquid chromatography and sensitive ELISA for marinobufagenin-like immunoreactivity. Moreover, the structural information was obtained by mass spectrometry. To determine the biological action, MBT (9.6 and 0.96 microg/kg per day) was intraperitoneally infused via an osmotic minipump for 1 week. Blood pressure and renal excretion of marinobufagenin-like immunoreactivity were measured. Marinobufagenin-like immunoreactivity was found in Y-1 cell culture media, and the concentration increased until 24 hours. The structural analysis suggested that marinobufagenin-like immunoreactivities were marinobufagenin and MBT, and tandem mass spectrum analysis revealed them with the specific daughter ions. The highest sensitive ELISA-positive peak of marinobufagenin-like immunoreactivity in the media was MBT. Continuous administration of MBT in rats for 1 week significantly increased systolic blood pressure and renal excretion of marinobufagenin-like immunoreactivity compared with control rats (135+/-3.0 versus 126+/-2.0 mm Hg and 1.41+/-0.286 versus 0.34+/-0.064 ng/day, respectively). These data suggest that MBT, arginine-suberoyl ester of marinobufagenin, can be a novel digitalis-like factor with hypertensive action and is secreted from the adrenocortical cells. (+info)
Analyses of biologically active steroids: antitumor active OSW-1 and cardiotonic marinobufotoxin, by matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight tandem mass spectrometry.
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Naturally occurring constituents of biological or pharmaceutical interest often exist in the form of glycosides or conjugates. Mass spectral investigations of these compounds require soft ionization techniques if information on molecular mass, sugar sequence, or conjugate content is desired. In this study, matrix-assisted laser desorption/ionization (MALDI) quadrupole ion trap (QIT) time-of-flight tandem mass spectrometry (TOF-MS(n)) was used to identify both OSW-1, an acetylated cholestane diglycoside showing antitumor activity, and the cardiotonic steroid, bufotoxin. Each molecular-related ion was identified, and subsequent collision-induced dissociation experiments in which a molecular-related ion was selected as a precursor ion produced the characteristic product ions that are essential for structural elucidation. OSW-1 and its analogue with a modified side chain, thienyl OSW-1, were synthesized, and bufotoxins, i.e., marinobufotoxin and its homologue, marinobufagin 3-pimeloylarginine ester, were isolated from toad venom. On MALDI-TOF-MS, sodium-adduct [M+Na](+) ions were observed in the steroid glycosides, although protonated [M+H](+) ions were relatively more abundant than sodium-adduct [M+Na](+) ions in the bufotoxins. On the basis of tandem MS results, we propose key fragmentation pathways. The sugar moiety or side chain from the precursor ion was eliminated in OSW-1. However, characteristic product ions originating from the cleavage of the side chain with an ester formation were observed in the bufotoxins. Post-source decay (PSD) on MALDI-TOF-MS is also described when evaluating alpha-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid as a matrix to obtain useful ions required for the identification of compound. (+info)
Photoaffinity labeling of the ouabain-binding site on (Na+ plus K+) adenosinetriphosphatase.
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An ethyl diazomalonyl derivative of cymarin was synthesized in order to photoaffinity label the cardiac glycoside-binding site on (Na(+) + K(+)) adenosinetriphosphate (EC 3.6.1.3). When a noncovalent complex of the enzyme and this cardiac glycoside derivative was photolyzed, a covalent bond was formed between the ligand and the larger of the two polypeptide subunits of the enzyme. Several control experiments demonstrate that this photochemical reaction occured while the ligand was bound to the site at which it inhibits the enzyme activity. Another specific inhibitor, tentatively identified as the ethyl chloromalonyl derivative of cymarin, produced similar photoaffinity labeling of the larger subunit, demonstrating that the photolytic dissociation of the diazo group may not be responsible for the photochemical reaction. Since the cardiac glycoside-binding site, which is accessible from the outside surface of the plasma membrane, and the phosphorylation site, which is accessible from the inside surface, are both on the larger polypeptide subunit of (Na(+) + K(+)) adenosinetriphosphatase, this polypeptide has sequences exposed to both sides of the membrane. (+info)
The action of digitonin on rat liver mitochondria. Phospholipid content.
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1. The amount and types of phospholipid and the fatty acid composition of the various phospholipids were examined in intact rat liver mitochondria, in mitochondria devoid of their outer membrane (preparation A) and in very small pieces derived from the disruption of the inner-membrane complexes (preparation B). The latter two preparations were obtained by digitonin treatment and carry out oxidative phosphorylation. 2. The ratio mug.atoms of phospholipid P/mg. of protein was 0.163 for intact mitochondria, decreased to 0.118 on removal of the outer membrane and increased markedly to 0.292 on disruption of the inner-membrane complex. 3. Examination of the various types of phospholipid present showed that the molar proportions cardiolipin:phosphatidylcholine:phosphatidylethanolamine were approx. 1:6:6 for intact mitochondria and 1:3:3 for preparations A and B. 4. There was a correlation between the recovery of cardiolipin and adenosine triphosphatase activity in the conversion of intact mitochondria into preparations A and B. 5. The fatty acid contents of the various types of phospholipid purified by thin-layer chromatography were identical in all three preparations. Our results show a considerably higher content of arachidonic acid and lower content of oleic acid for phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol than have previously been reported for mitochondrial phospholipids. (+info)
Fluorometric measurement of pyridine nucleotide reduction in the giant axon of the squid.
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By monitoring the fluorescence of the isolated giant axon of the squid Loligo pealei, it was possible to follow changes in its oxidation-reduction state as caused by the action of anoxia, cyanide, Amytal, and azide. The response to oxygen depletion was very rapid, the NAD within the axon being 90% reduced within 1-2 min. Cyanide and Amytal gave essentially similar results, although somewhat longer periods of time elapsed during their onset and washout periods. The extent of NAD reduction was essentially the same under conditions of anoxia and treatment with cyanide and Amytal. Azide was less effective in this respect, and at comparatively high levels of concentration (25-50 mM) gave values of 40% or less of the reduction observed with the other inhibitors. The application of ouabain and strophanthidin gave no observable NAD reduction. Variations in the time required to consume given quantities of dissolved oxygen before and after stimulation indicated an increase of 10-20% in oxygen uptake rate associated with activity, although this figure appeared to be a function of the surface-to-volume ratio of the axon. A biochemical analysis of axoplasm for oxidized and reduced pyridine nucleotide was made. Fluorometric examination of centrifuged axoplasm indicated that the NAD-NADH was largely confined to the mitochondria of the axon. (+info)