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PubMedDate not supplied

Further studies on the properties of bile acids. II. Effect of bile acids on the reactivity of adrenergic and cholinergic receptors in rat intestine.

The effects of bile acids (deoxycholic, cholic and dehydrocholic) were studied on the action of certain autonomic system drugs (isoprenaline, adrenaline, noradrenaline and acetylcholine). It was also tried to explain the causes of these changes in the light of the results of experiments with the widely used antagonists of adrenergic and cholinergic receptors. The experiments were carried out on isolated rat intestine by the method of Magnus. It was found that bile acids decreased the relaxing effect of isoprenaline and caused inversion of the action of adrenaline and noradrenaline on the intestine. Changes in the action of catecholamines are caused by stimulation of alpha-adrenergic receptors enhanced by bile acids, with a simultaneous decreased stimulation of beta-receptors. Bile acids cause also an increase of the effect of acetylcholine on the intestine.

Animals↗
PubMed1983

[Spasmolytic activity of (3,4-dichloroanilino)phenylacetonitrile (H 74) and its analogs].

The influence of smooth muscle contractility of (3,4-dichloranilino)phenyl-acetonitrile (H 74) was studied in comparison with the analogs (4-chloranilino)phenyl-acetonitrile (H 47) and (3,4,5-trichloranilino)phenyl-acetonitrile (H 84) and several standard pharmaca. H 74 and H 84 showed a spasmolytic action that was almost equal to that of methphenethamine and papaverine. Other investigations have revealed that H 74 was free from any side effect. It is concluded that chloranilino-phenyl-acetonitriles cause a nonspecific inhibition of smooth muscle contractility.

Acetonitriles↗
PubMed1984

[Calcium antagonism by papaverine in isolated rat gastric fundus strips in a model system].

Examining isolated strips of gastric fundus tissue of rats the authors observed that papaverin up to 7.8 X 10(-8) to 6.25 X 10(-7) mol/l increased the intensity of convulsions induced by constant amounts of barium chloride (9.5 X 10(-4); with further increase of the concentration the intensity of convulsions gradually sank under the initial value. An increased proneness to cramping was also observed when the calcium content of the Tyrode solution was reduced. In this case the proneness to cramping was highest between 1 and 1.3 mmol/l calcium content. When the calcium content was 1 mmol/l, papaverin increased the proneness to cramping only to a smaller degree, in agreement with the effect measured when the calcium content of the organ bath was reduced below 1 mmol/l. In model experiments, calcium antagonized the potential difference-increasing effect of papaverin at the ether/NaCl (0.1 mol/l) phase boundary. From this the authors infer an interaction (complex formation) between papaverin and calcium at the phase boundary, which is independent of the biological medium. Their findings and the papaverin -calcium antagonism first observed by Benigni [2] can be interpreted in this way.

Animals↗
PubMed1981

Reactivity of isolated digital arteries in hypertension.

To see whether the increased peripheral vascular resistance seen in human hypertension is due to an altered reactivity of vascular smooth muscle, strips of digital arteries obtained post mortem from 13 hypertensive have been compared with those from 13 normotensives. The strips from the hypertensives were significantly thicker than those from the normotensives, as were those from male patients compared to females. This was reflected in a significantly greater response of the strips from the hypertensives and males to 80 mM KCl. The maximum responses to noradrenaline and 5-hydroxytryptamine, but not the concentrations required to produce 50% of the maximum responses, were significantly smaller in the strips from hypertensives than in those from normotensives. There were no significant differences between the strips from hypertensives and normotensives in either the maximum responses to angiotensin or barium chloride, or the concentration of those agonists required to produce 50% of the maximum response. It is concluded that the decreased reactivity to noradrenaline of the hypertensive vessels may be a sequel of either the increased pressure itself or increased exposure in vivo of the blood vessels from hypertensives to noradrenaline.

Angiotensin II↗
PubMed1981

Spasmolytic effect of lidamidine on uterine smooth muscle.

1-(2,6-Dimethylphenyl)-3-methylamidinourea hydrochloride (lidamidine hydrochloride) has previously been reported to inhibit intestinal smooth muscle contractile activity in vivo and in vitro. This study showed lidamidine also inhibited contractile activity in the isolated gravid rat uterus preparation and antagonized, the spasmogenic effects of acetylcholine, serotonin, oxytocin, and PGF2 alpha and BaCl2. Increasing Ca2+ concentrations in the bathing medium from 0.9 mmol/l to 7.2 mmol/l effectively antagonized the lidamidine inhibition of responses to BaCl2 and acetylcholine in the gravid rat uterus preparation. These results suggest that the spasmolytic effect of lidamidine may be due to its interference with the availability of Ca2+ necessary for excitation-contraction coupling in smooth muscle.

Acetylcholine↗
PubMedDate not supplied

[Electrophysiologic effects of magnesium chloride on the Purkinje fibers of the dog].

In order to relate the cardiac antiarrhytmic properties of magnesium chloride (MgCl2) to its electrophysiological effects, a comparison of its actions on three different models of automaticity of the isolated Purkinje fibers of the dog, has been carried out. The spontaneous activity of the Purkinje fibers perfused with Tyrode's solution containing 2.7 mM KC1 was gradually reduced as MgC12 concentration was increased from 3 to 9 mM/1. The automaticity induced adding barium chloride (BaC12) to the perfusion solution was suppressed increasing the concentration of MgC12 in the Tyrode's solution up to 5 mM/1. Previous increases in the concentration of MgCl2 prevents the electrophysiological effects BaC12. The negative chronotropic effects of MgC12, were less evident on the adrenalin induced automaticity of the Purkinje fibers. Simultaneous addition of adrenalin and MgC12 to the perfusion media increases membrane resting potential action potential amplitude and maximun rate of depolarisation of phase O in Purkinje fibers. It is concluded that MgC12 acts by distinct electrophysiological mechanisms against the different models of cardiac automaticity studied. This findings may provide interesting perspective in respect to the therapeutic properties of magnesium chloride.

Animals↗
PubMed1982

[The effect of oxytocin on contractility of the human uterine artery].

We have studied in this work 30 human uterine arteries which were taken from hysterectomy specimens where the indication for the hysterectomy was obstetrical or gynaecological. The arteries were prepared in strips using furchgott and Bhadrakom's technique that they developed for the isolated aorta of the rabbit so that the authors could study the response to oxytocin on the isolated human uterine artery. When CIK was added to the preparation in which the arteries were, oxytocin had an antagonistic effect which was dose-dependent. The same effect was noted when Cl2Ba was added.

Adult↗
PubMed1980

Subchronic oral toxicity of BaCl2 in rats.

Groups of young adult rats of both sexes were exposed to 0, 10, 50, or 250 mg/liter (ppm) of barium as barium chloride in drinking water for 4, 8, or 13 weeks. No adverse effects related to barium ingestion were observed in food consumption, clinical signs, body weight, hematologic parameters (i.e., hemoglobin, hematocrit, red cell count, leukocyte count, prothrombin time, and fibrinogen), serum enzyme activities (i.e., SGOT, SGPT, and blood urea nitrogen), serum ions (i.e., Na, K, and Ca), gross pathology, and histopathology. Water consumption was slightly depressed in the highest dose group. A slight decrease in the relative weight of adrenals of treated vs. control animals was observed. Increasing dose, but not duration of exposure, produced related increases in barium concentrations in liver, skeletal muscle, heart, and bone, with the highest concentrations observed in bone.

Animals↗
PubMedDate not supplied

Antiarrhythmic properties of Craviten (M-71) in cats and rabbits.

Preparation M-71 (Craviten, Polfa) possesses strong antiarrhythmic properties. It prevents development of cardiac arrhythmia evoked by BaCl2, ouabain and adrenaline in cats and rabbits, and abolishes the already developed arrhythmias. It prevents the aconitine-evoked arrhythmia only in rabbits.

Aconitine↗
PubMed1981

Calcium-based evaluation of dose-response curves of papaverine-like relaxants in guinea-pig taenia coli.

Using CaCl2 dose-contraction curves in 165.6 mM K(+)- depolarized guinea-pig taenia coli, the maximal contraction level induced by 30 mM CaCl2, and the maximal relaxation level induced by Ca-free solution were treated and 0% and 100% relaxation, respectively. Then four kinds of contraction level were compared: (1) the normal level, (2) 5.5 microns acetylcholine (ACh)-induced contraction, and (3) 1.65 mM ACh- or 3 mM BaCl2-induced contraction in normal solution; and (4) 2.2 and 30 mM CaCl2-induced contraction in K(+) depolarizing solution. The relaxing effects of papaverine, MnCl2, and isoproterenol at these different contraction levels were compared. Papaverine- and MnCl2-induced relaxation of the higher contraction levels [a part of (2), (3) and (4)] seem to reflect a mechanism of the intracellular calcium mobilization, being quite different from relaxation induced by papaverine-like relaxants and isoproterenol at the lower contraction levels [(1) and part of (2)]. The latter phenomenon seems to reflect mechanisms related to cyclic AMP. Papaverine inhibited competitively BaCl2-induced contraction only in K(+) depolarized tissues, suggesting a mechanism of direct reaction with the intracellular Ca store.

Acetylcholine↗
PubMed1980

Snake venom phospholipases A2. A fluorescence study of their binding to phospholipid vesicles correlation with their anticoagulant activities.

The interaction of snake venom phospholipases A2 with phospholipids has been studied by intrinsic fluorescence. This has been performed in order to understand why some enzymes possess anticoagulant properties while others have no action on blood clotting. We show that phospholipases A2 can be distinguished according to their binding properties to phospholipid vesicles. Strong inhibitors of coagulation interact with phospholipids with a significant change of their fluorescence while poor inhibitors have little or no effect. Strong inhibitors have a great affinity toward phosphatidylserine and do not require Ca2+ for interaction. Similar results are obtained with phosphatidylcholine-phosphatidylserine 1:1 mixtures. The diether analogue of phosphatidylcholine shows that formation of the complex is promoted by Ca2+ and can occur whenever the lipids are in crystal or fluid phase. Inactivation of anticoagulant phospholipase A2 decreased the affinity of enzyme for the phospholipids. The change in the intrinsic fluorescence of the phospholipases A2 on binding indicates a modification of the environment of the tryptophan residues. This is discussed in terms of the so-called interface recognition site as seen in the case of pancreatic phospholipase A2. It is concluded that the phospholipases may inhibit coagulation by competing with clotting proteins for the lipid surface. Although not considered in this study, the consequence of the hydrolysis of lipids remains to be estimated.

Animals↗