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PubMed1980

Cardio-selective beta adrenergic stimulation with prenalterol in the conscious dog.

The effects of cardioselective beta-1 adrenergic agonist, 1-(4-hydroxyphenoxy)-isopropylamino-2-propanol), i.e., prenalterol, were examined on direct and continuous measurements of left ventricular (LV) pressure, diameter, dP/dt, velocity of shortening, arterial pressure, iliac blood flow and heart rate in 10 conscious dogs. Prenalterol was infused on 3 separate days in doses of 1, 2 and 4 micrograms/kg/min for 15 min. The largest dose of the drug increased LV/dP/dt by 70 +/- 7% from 3581 +/- 130, velocity of LV shortening by 27 +/- 4% from 86 +/- 7 mm/sec, heart rate by 51 +/- 9% from 80 +/- 5 beats/min and iliac blood flow by 40 +/- 4% from 134 +/- 15 ml/min and decreased LV end-diastolic diameter by 8 +/- 2% from 35 +/- 2 mm and LV end-systolic diameter by 15 +/- 2% from 24 +/- 2 mm. All these responses were significant, P < .01. Mean arterial pressure did not change. The positive inotropic effects persisted for 1 hr. The lowest dose of the drug studied increased LV dP/dt and velocity but not heart rate. Practolol, a beta-1 adrenergic receptor blocker, prevented the positive inotropic effects and the increases in iliac blood flow indicating that prenalterol exerts its cardiovascular actions primarily by stimulation of beta-1 adrenergic receptors.

Adrenergic beta-Agonists↗
PubMed1981

[Review: beta-blocking agents in dermatology (author's transl)].

The authors present a survey of the side effects of beta-blocking agents. Practolol has been linked with a lupus syndrome characterized by biological abnormalities and eventually clinical signs; later on, other beta-blocking agents have been able to induce such manifestations. Thus, all beta-blocking agents proved hazardous and they must be prescribed with extreme caution in patients with immunological imbalance. Furthermore, pruritus and lichenoid or psoriasiform dermatitis have been documented. This must be kept in mind in the presence of any unspecific rash in elderly patients.

Adrenergic beta-Antagonists↗
PubMed1981

Deliberate hypotension for middle ear microsurgery.

By means of groups of one hundred patients undergoing middle ear microsurgery, we compared two hypotensive anesthesia techniques combining halothane, a non-depolarising myorelaxant and a beta adrenoreceptor blocking agent. Practolol, a beta 1 receptor blocker was administered to the patients of group A while those of group B received labetalol, a more recently introduced alpha and beta receptor blocker. The duration of microsurgery for each type of pathology was identical in both groups but the operation conditions (mostly the amount of bleeding) were better in group B (statistically significant). Moreover, the mean delivered halothane concentration could be reduced by 20% (from 0.85% to 0.68%). Thirty patients undergoing tympanoplasty were followed up for several months to determine the the importance of peroperative conditions in relation to the functional result of these operations. Excessive bleeding hinders the surgeon and the positioning of the implant and also, as confirmed by this study, makes the success of the tympanoplasty uncertain. Two factors likely to predispose the patient to bleeding (and able to be brought under control preoperatively) have been highlighted: these are overweight (obese status about 80 kg) and a systolic arterial blood pressure at rest above 140 torr. The various agents which were used and the reasons for their choice are discussed.

Adrenergic beta-Antagonists↗
PubMed1980

Variability in the preventive action of the B-blockers on genetic hypertension in the rat.

Changes in arterial blood pressure were compared in young male SHR rats untreated or treated orally with a beta-blocker for 5 days out of 7 from the 5th to 9th week of life. Propranolol, acebutolol and practolol, at a daily dose of 50 mg/kg, prevented the occurrence of hypertension, not only during the 4 weeks of treatment, but also during 6,9 and 11 weeks respectively after cessation of treatment. Alprenolol and metoprolol (50 mg/kg/day) and atenolol (100 mg/kg/day) proved to be active only during the period of treatment, whereas oxprenolol (100 mg/kg/day) was totally inactive. Propranolol and acebutolol were, however, inactive under identical conditions with SHR of the same strain but bred in another laboratory. The physiological difference between the two groups of SHR was confirmed by the fact that the resistance of their erythrocytes to osmotic shock was different. This suggests that all the beta-blockers do not necessarily have the same preventive activity with respect to hypertension in the SHR and that two groups of SHR bred in two different places can be physiologically dissimilar even though they originate from the same strain.

Acebutolol↗
PubMed1982

Liver tumors induced by a new beta-adrenoreceptor blocking agent in female rats.

A newly synthesized beta-adrenoreceptor blocking agent, DL-1-(2-nitro-3-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1305), administered intragastrically for 6 months induced hepatocellular carcinomas in female outbred Wistar rats in a dose-dependent fashion but was harmless to the livers of male outbred Wistar rats. Experiments with castrated animals confirmed the dependence of the carcinogenic effect of ZAMI 1305 on the hormonal status of the rat. When an isomer of ZAMI 1305, DL-1-(2-nitro-5-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1327), and DL-practolol, which have pharmacologic activities similar to those of ZAMI 1305, were administered by the same experimental technique as used for ZAMI 1305, no liver tumors appeared either in male or female rats.

Adrenergic beta-Antagonists↗
PubMed1984

Adrenergic receptors and gastric secretion in dogs. Is a "tonic balance" relationship between vagal and beta 2-adrenergic activity a possibility?

The relative influence of adrenergic receptors on gastric acid secretion in the dog stomach with different vagal activity or "tone" is almost unknown. beta-adrenoceptors seem to be most important for the direct effect of adrenergic stimulation on acid secretion. In this study the effects of vagotomy and beta 2-adrenoceptor activity were studied in conscious gastric fistula dogs. Pentagastrin stimulated acid output was increased slightly in non-vagotomized dogs and to its prevagotomy level in vagotomized dogs after propranolol infusion. Practolol showed no such effect. Histamine stimulated acid secretion was not influenced significantly by beta-blockade. Similar dose-response curves were found for non-vagotomized dogs with high beta 2-adrenergic tone and dogs with low vagal tone (vagotomy) after pentagastrin and histamine stimulated acid secretion. This study indicates that a counterbalance between beta 2-adrenergic and cholinergic vagal tone exists. A "tonic balance theory" is suggested and is probably involved in the resulting acid secretion after vagotomy.

Adrenergic beta-Antagonists↗
PubMed1984

Dopaminergic and beta-adrenergic effects on gastric antral motility.

Stimulation of splanchnic nerves and application of adrenergic drugs have been shown to give variable effects on gastric motor activity depending especially on the background activity. beta-adrenoceptors and dopaminergic receptors mediate inhibitory effect on proximal gastric motor activity. The purpose of the present study was to evaluate the effects of isoprenaline, a beta 1- and beta 2-agonist, and dopamine on gastric antral motility in gastric fistula dogs. Dopamine was used alone and in conjunction with selective blockade of adrenergic and dopaminergic receptors during infusion of bethanechol or pentagastrin inducing motor activity patterns as in the phase III of the MMC and the digestive state respectively. The stimulated antral motility was dose-dependently inhibited by dopamine. The effect was significantly blocked by specifically acting dopaminergic blockers, while alpha- and beta-adrenergic blockers were without any significant effects. Dose-response experiments with bethanechol and dopamine showed inhibition of a non-competitive type. Isoprenaline was used alone and in conjunction with selective blockade of beta 1- and beta 2-receptors during infusion of bethanechol which induces a pattern similar to phase III in the migrating myoelectric complex. The stimulated antral motility was dose-dependently inhibited by isoprenaline. The effect could be significantly blocked by propranolol (beta 1 + beta 2-adrenoceptor blocker) and by using in conjunction the beta 1-adrenoceptor blocker practolol and the beta 2-adrenoceptor blocker H 35/25. The dose-response experiments showed inhibition of a non-competitive type. These studies indicate that gastric antral motility is inhibited by isoprenaline through both beta 1- and beta 2-receptors and by dopamine through specific dopaminergic receptors.

Adrenergic beta-Agonists↗
PubMedDate not supplied

[Importance of catecholamines and various subtypes of beta-adrenoreceptors for resistance of mice to acute, intensive cooling].

A phase dynamics in body temperature and thermoproduction was shown in the course of cooling of mice. 3 periods of various intensity were noted in thermocompensatory reactions. Within the first period content of noradrenaline was maintained in the vitally important tissues (brain, heart and brown adipose tissues); later on the content of noradrenaline was distinctly decreased. The blockade of ganglions and beta-adrenoreceptors inhibited markedly the thermoproduction and resistance to cooling. The main thermocompensatory reactions were realized via beta 1-adrenoreceptors; blocking of beta 1-adrenoreceptors by means of practolol was more effective as compared with the influence of N-isopropylmethoxamine--inhibitor of beta 2-adrenoreceptors. Importance of beta 1-adrenoreceptors in thermoregulation is discussed.

Acclimatization↗
PubMed1983

Role of beta-1 adrenergic receptors in the control of the heterogeneity of O2 saturation in small myocardial veins.

The role of beta adrenergic receptors in the control of venous O2 saturation heterogeneity was studied in the left ventricular free wall of 24 anesthetized open-chest dogs. Venous and arterial O2 saturation was obtained microspectrophotometrically and combined with radioactive microsphere blood flow determinations to calculate regional myocardial O2 consumption. The mean and variance of venous O2 saturation were determined under six experimental conditions designed to produce graded levels of beta adrenergic activity. Regional O2 consumption, extraction and flow were also determined. Propranolol, 2 mg/kg, significantly lowered the O2 saturation variance in both small subepicardial and subendocardial veins compared to control. Isoproterenol, 10 micrograms/kg/min, did not alter the variance of venous O2 saturation. Isoproterenol, 10 micrograms/kg/min, in the presence of 2 mg/kg of propranolol was able to prevent the reduction in variance of venous O2 saturation seen with propropranolol alone. However, 0.1 microgram/kg/min of isoproterenol did not prevent this fall in venous O2 saturation variance with propranolol. Practolol, 1 mg/kg, also caused a significant fall in venous O2 saturation variance in the subepicardium and subendocardium. From this it can be concluded that there is an inhomogeneous distribution in beta-1 adrenergic receptor population and/or activity in the left ventricle. Thus, there appear to be small regions in the heart with high O2 consumption and extraction related to beta-1 adrenergic activity and/or distribution.

Animals↗
PubMed1984

Beta adrenoreceptors in the rabbit bladder detrusor muscle.

This study examines the beta adrenergic receptors of the rabbit detrusor smooth muscle, employing [125I]iodocyanopindolol (ICYP) as a ligand for the binding of beta adrenergic receptors. Saturation binding experiments on the isolated membrane fraction yielded a KD for ICYP of 14.7 pM and a maximum binding of 147.6 fmol/mg of protein. Displacement of labeled ICYP by a series of beta adrenergic agents yielded the following KD values for the combined high and low affinity binding sites: I-propranolol, 0.76 nM; ICI 118,551, 1.7 nM; zinterol, 38.0 nM; metoprolol, 3.5 microM; and practolol, 61.4 microM. When these displacement experimental results were compared to KD values from other reported binding studies with ICYP for beta adrenoreceptors, both the order of potency and the KD values indicated primarily beta-2 adrenergic receptor subtypes. Computer program Scatfit analysis of the displacement curves indicated a single slope and affinity constant for all five beta adrenergic agents. Hofstee plots for zinterol, ICI 118,551 and metoprolol, however, were not linear and indicated that minor populations of beta-1 adrenoreceptors were also present as both high and low affinity binding sites could be defined. It is concluded that the primary receptor population is beta-2 and that this tissue is heterogenous with a small population of beta-1 adrenoreceptors representing approximately 13 to 23% of the total beta adrenoreceptor population.

Animals↗
PubMed1978

Effect of isoproterenol on myocardial creatine kinase activity in rats.

Isoproterenol (0.1-500 mg/kg) decreased the myocardial creatine kinase (CK) activity in rats. The maximum effect was already reached with 10 mg/kg, decreasing the enzyme activity to 58.5% of the control values. The beta-blocking agents propranolol and practolol, and also glucocorticosteroids inhibited the isoproterenol effect. The relative CK isoenzyme composition of the myocardium was not grossly altered by isoproterenol, as shown by DEAE-Sephadex A-50 macrocolumn chromatography. --Serum CK was increased significantly after the administration of the excessive dose of 500 mg isoproterenol/kg.

Animals↗
PubMed1978

Direct measurement of myocadial hardness.

Myocardial hardness, defined as resistance to a pitting force, was measured on several sites of the myocardium in 20 anesthetized dogs. The durometer used for hardness measurements consisted of an indentor, 4 mm in diameter, pressed perpendicularly on the myocardium by a calibrated spring (elastic modulus 325 N/m). Hardness changes during the cardiac cycle caused movement of the indentor which interrupted a light beam falling on a photoresistance. Changes in illumination of the photoresistance resulted in resistance changes, which were recorded using a Wheatstone bridge and a DC amplifier. Hardness was expressed in mm of spring shortenings. Balanced in (zero hardness), the indentor protruded 7.2 mm beyond the foot. Thus hardness adequate to press the indentor level with the foot defined as 7.2 mm. The left ventricular pressure (LVP) rise followed slightly the hardness rise (from 29.5 +/- 3.6 msec--mean +/- SEM--for the basal area at the right ventricle to 35.8 +/- 5.9 msec for the basal area of the left ventricle. Apical areas were significantly harder in systole than corresponding basal areas and left ventricular areas had a significantly higher systolic hardness (SH) than corresponding right ventricular areas. Changes in LVP by transfusion bleeding caused almost proportional changes in SH. While using a constant pressure reservoir in left atrium and another in aorta, adrenaline caused a significant increase in SH, decrease in diastolic hardness (DH) and increase in hardness width (WH); calcium chloride caused a nonsignificant increase in SH and WH and a significant decrease in DH; practolol caused a nonsignificant decrease in SH and a significant increase in DH and decrease in WH. Ligation of 3--5 branches of the anterior descending coronary artery resulted in a significant increase in DH and reduction in the WH distally to the ligation during the first 11 min. The WH was significantly reduced as a function of time in both areas (healthy and infarcted) taken collectively. The WH was significantly higher over the healthy area than over the infarcted one at corresponding times.

Animals↗
PubMed1984

Physical exercise inducing electrophysiological changes in the atria: sympathetic-mediated effects?

Rats were subjected to long-term physical exercise by swimming and their hearts were examined electrophysiologically in order to identify relevant factors as mechanisms of protection from rhythm disturbances. The role of catecholamines was also studied using a chronically applied beta-adrenergic blocking drug, Practolol, or a catecholamine depleting drug, Reserpine. The results were compared with those obtained in rats similarly injected but kept in sedentary life. Action potential duration was found to be prolonged in trained animals regardless of the drug employed. Trained animals showed increments in the myocardial mass. Prolongation of the action potential coincided with lower values for maximum follow frequencies. It is suggested that the effects elicited could protect the heart against rhythm disturbances. The sympathetic nervous system seemed to play no important role.

Animals↗
PubMedDate not supplied

[Effect of cordarone on blood circulation under general anesthesia and in free behavior].

Experimental data on the effect of cordarone (10 mg/kg) upon blood circulation in animals under general anesthesia and in free behavior are presented. It was established that under general anesthesia cordarone induced in animals hypotension (16 +/- 2%), bradycardia (19 +/- 1.82%), heart contractility inhibition (29 +/- 6.10%). In animals under conditions of free behavior cordarone causes hypertension (9 +/- 3.1%), tachycardia (11 +/- 1.3%) and potentiates cardiac contractility. Practolole, a selective beta1-adrenoblocking agent, potentiates the effect of cordarone on the myocardium and also obliterates the difference between the effects of the drug in animals under general anesthesia and in free behavior. These data point to the drug exerting a direct inhibitory effect on the myocardium. It is suggested that the difference in the effects of cordarone in animals under general anesthesia and in conditions of free behavior is due to a lesser degree of activation produced by the drug in anesthetized animals.

Amiodarone↗
PubMed1978

[Assessment of early arrhythmias in acute experimental myocardial infarct in rabbits].

Arrhythmias were studied at the early stage after rapid ligation of the left ventricular artery on an experimental model of arrhythmia in rabbits. The rabbits were subjected to thoractomy and ligation of the left ventricular artery under direct visualization. The electrocardiographic and hemodynamic parameters were recorded. Electrocardiographic signs of infarction and changes in rhythm were recorded in 60% of the animals. The rate of cardiac contractions and the arterial pressure decreased after the ligation. In the group in which practolol was applied the rate of arrhythmias dropped to 25%. The effect of adrenergic beta-block on acute occlusion of the coronary artery is discussed.

Acute Disease↗
PubMed1978

Vagal stabilization of the ischemic canine ventricle.

To determine whether vagal activity during myocardial ischemia functions to stabilize the heart, the left anterior descending coronary artery in dogs was occluded for periods of 3 1/2 minutes with and without concurrent vagal stimulation. Bipolar electrograms were measured from the surface of the canine left ventricle within and outside the regions of intended ischemia. Ischemia in the absence of vagal stimulation depressed both the electrogram amplitude and the upstroke velocity of the electrogram signal. Vagal stimulation significantly decreased the absolute magnitude of the ischemia-induced decrease of the electrogram signal, which indicates that it tended to stabilize the insulted heart. This stabilizing influence however, was seen only in the presence of adrenergic blockade with practolol. The vagal response was only partially blocked by atropine, whereas it was abolished by lidocaine. These results suggest that a vagally mediated stabilization of the ischemic canine ventricle can occur and is unmasked only in the absence of sympathetic neural activity.

Animals↗
PubMed1975

[Pharmacokinetics of acebutolol].

Pharmacodynamic data correlating beta-adrenoceptor blockade with plasma level of drug were obtained in healthy male volunteers (3). Direct comparison of the inhibition of isoprenaline induced tachycardia was achieved in each volunteer after the administration of single doses of either acebutolol (300 mg), practolol (400 mg) or propranolol (40 mg). These drugs were approximately equipotent at these doses, at the times of maximum beta-adrenoceptor blockade. Pharmacokinetic data were obtained in hypertensive male patients (4) after treatment with 14C-radioactively labelled acebutolol hydrochloride. Both 'total-14C' levels and specific '14C-acebutol' levels were determined in plasma, urine and faeces. It was shown, by calculation from the renal clearance, that the late biological half-life for the decline of 14C-acebutolol in plasma was 9.4 h and 13.2 h, respectively, in two of these patients treated with a single oral dose (200 mg) of 14C-acebutolol hydrochloride. In one of the patients treated by intravenous infusion (20 mg/10 mn), the late biological half-life plasma was calculated to be 7.5 h. Renal clearance of acebutolol was shown to be close to a mean of 83 ml plasma/mn for each of three patients (two oral and one intravenous) in spite of the fact that one of the orally treated patients had an elevated level of urea in his plasma (47 mg/100 ml) indicative of some impairment of kidney function. The recovery of 14C-radioactivity in the urine (29 p. cent) and faeces (64 p. cent) was 93 p.cent of the dose of labelled acebutolol in one of the orally treated patients. The overall proportion of the dose excreted as unchanged 14C-acebutolol was 62 p.cent. The major metabolite was the product formed by shortening of the butyramido-group of acebutolol to form an acetamido-group. This metabolite was also readily excreted in both urine and faeces and was also detected in an extract of the 4 h plasma from an orally treated patient. It was identified by co-chromatography as the acetyl analogue (M & B 16 942) of acebutolol. It would be detected by the colorimetric assay of acebutolol in plasma because the same aromatic amino-compound (M & B 17 127) would be formed during the acid hydrolysis procedure. A small quantity of an other unidentified metabolite was detected in an extract of freeze-dried urine after autoradiography of a two dimensional thin layer silica-gel chromatogram.

Acebutolol↗
PubMed1993

Effect of levamisole hydrochloride on the guinea-pig atrium.

The effects of levamisole on the guinea-pig atrial preparation were determined. At 3 micrograms/ml, levamisole and lignocaine prevented electrically induced arrhythmia in 3 and 5 out of 5 preparations respectively. It was concluded that levamisole at the therapeutic anthelmintic dose would not abolish clinical atrial arrhythmia. Levamisole even at 3 micrograms/ml had definite salutary effect on the hypodynamic state induced by continuous electrical stimulation. The dose-related positive inotropic effect of levamisole 5-200 micrograms/ml was not antagonised by practolol but was absent in atria from reserpinized animals. Therefore, cAMP may not be involved in the positive inotropic effect. Levamisole antagonised verapamil-induced negative inotropic effect and no positive inotropic effect was observed when the Ca2+ content of the Ringer-Locke solution was below normal. These suggested that Ca2+ must be involved in the inotropic effect. The negative chronotropic effect due to levamisole was not antagonised by hexamethonium but was antagonised by atropine, thus indicating that stimulation of M1 or M2 receptors in the atria may be responsible.

Animals↗