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PubMed1979

Influence of biogenic amines on the growth of xenografted human colorectal carcinomas.

The influence of some biogenic amines and amine-receptor-blocking drugs in the growth rate of human colorectal carcinomas propagated as s.c. xenografts in immune-deprived mice was studied. In mice treated with adrenaline, a beta-adrenergic agonist, the growth of xenografts was suppressed for 2 days, after which growth was resumed at a rate similar to that in control animals. Treatment with the phosphodiesterase inhibitor theophylline prolonged the adrenaline-induced inhibition of growth. Treatment with the beta-adrenergic antagonist sotalol or practolol increased the rate of tumour growth. Treatment with either serotonin or the histamine H2-receptor agonist Dimiprit had no effect on tumour growth rate. However, the antiserotoninergic drug BW 501C and the histamine H2-receptor antagonist cimetidine each caused short-term suppression of tumour growth.

Adrenergic Agonists↗
PubMed1981

Measurement of partial agonist activity of pindolol.

The partial agonist activity of pindolol was assessed by examining the action of cumulative doses on the heart rate of resting, standing, and exercising healthy men and by studying the interaction of pindolol with metoprolol, a beta blocker devoid of partial agonist activity. Pindolol did not affect resting or standing heart rates (RHR, SHR) but reduced the heart rate after vigorous exercise by approximately 25%. The flatter dose-response curve of pindolol for exercise heart rate (EHR) has been reported from practolol and oxprenolol, which also exert partial agonist activity. After extremely large doses of pindolol there was no evidence of enhancement of agonist activity on RHR, nor was there any evidence of dominance of agonist activity over antagonist activity on EHR. Metoprolol did not alter RHR but reduced SHR by approximately 20% and EHR by approximately 31%. The effects of pindolol on SHRs and EHRs were not enhanced by metoprolol, even though the drug itself induced greater reductions of both. The reduction of SHR by metoprolol was reversed by pindolol. Pindolol appears to have greater affinity than metoprolol for atrial beta adrenoceptors in man.

Adult↗
PubMed1976

Protein phosphorylation in respiring slices of guinea-pig cerebral cortex. Evidence for a role for noradrenaline and adenosine 3':5'-cyclic monophosphate in the increased phosphorylation observed on application of electrical pulses.

1. Exposure of slices of cerebral cortex from guinea pigs to electrical pulses for 10s or to noradrenaline, 5-hydroxytryptamine or histamine increases the rate of phosphorylation of unidentified proteins in the tissue; the increases in protein phosphorylation due to electrical pulses and noradrenaline were non-additive, whereas the increases due to pulses and 5-hydroxytryptamine or histamine were additive. 2. The stimulating effects of electrical pulses and noradrenaline on protein phosphorylation were antagonized by the beta-adrenergic blocking agents L-propranolol, dichloroisoprenaline, practolol and ICI 66082, but not by the alpha-adrenergic blocking agents, phentolamine and phenoxybenzamine. 3. The increase in protein phosphorylation associated with electrical pulses was antagonized by 10 mum-trifluoperazine and 0.5 mum-prostaglandin E1. 4. It is postulated that under the experimental conditions used the action of electrical pulses on protein phosphorylation is mediated by noradrenaline acting through a beta-adrenergic receptor mechanism probably involving adenylate cyclase.

Adrenergic alpha-Antagonists↗
PubMed1976

Within-patient comparisons between different anti-hypertensive drugs.

1. By substituting one anti-hypertensive drug for the other in a panel of hypertensive patients equipotent doses have been determined. 2. Thus 40 mg of propranolol is equivalent to 4-5 mg of pindolol, 98 mg of practolol, 128 mg of alprenolol, 49 mg of metoprolol, 42 mg of tolamolol and 4-4 mg of timolol. 3. Bendorfluazide (10 mg) is eqivalent to 1-6 mg of bumetanide, 20 mg of chlorthalidone, 35 mg of mefruside and 3-5 mg of amiloride together with 35 mg of hydrochlorthiazide. 4. Methyldopa (250 mg) is equivalent to 6-0 mg of debrisoquine and 0-5 mg of St 600 (Boehringer), which is a clonidine-like substituted imidazoline.

Adrenergic beta-Antagonists↗
PubMed2004

Application of data mining techniques in pharmacovigilance.

AIMS: To discuss the potential use of data mining and knowledge discovery in databases for detection of adverse drug events (ADE) in pharmacovigilance. METHODS: A literature search was conducted to identify articles, which contained details of data mining, signal generation or knowledge discovery in relation to adverse drug reactions or pharmacovigilance in medical databases. RESULTS: ADEs are common and result in significant mortality, and despite existing systems drugs have been withdrawn due to ADEs many years after licensing. Knowledge discovery in databases (KDD) is a technique which may be used to detect potential ADEs more efficiently. KDD involves the selection of data variables and databases, data preprocessing, data mining and data interpretation and utilization. Data mining encompasses a number of statistical techniques including cluster analysis, link analysis, deviation detection and disproportionality assessment which can be utilized to determine the presence of and to assess the strength of ADE signals. Currently the only data mining methods to be used in pharmacovigilance are those of disproportionality, such as the Proportional Reporting Ratio and Information Component, which have been used to analyse the UK Yellow Card Scheme spontaneous reporting database and the WHO Uppsala Monitoring Centre database. The association of pericarditis with practolol but not with other beta-blockers, the association of captopril and other angiotensin-converting enzymes with cough, and the association of terfenadine with heart rate and rhythm disorders could be identified by mining the WHO database. CONCLUSION: In view of the importance of ADEs and the development of massive data storage systems and powerful computer systems, the use of data mining techniques in knowledge discovery in medical databases is likely to be of increasing importance in the process of pharmacovigilance as they are likely to be able to detect signals earlier than using current methods.

Data Collection↗
PubMed1997

Pharmacological characterization of adrenoceptors in horse corpus cavernosum penis.

1. The presence and types of alpha and beta-adrenoceptors in the corpus cavernosum of the horse were studied in vitro by using selected ligands of adrenoceptors and isometric tension recording. 2. Noradrenaline and phenylephrine induced concentration-dependent contractions in corpus cavernosum preparations. B-HT 920 had no effect. 3. Phentolamine and prazosin produced a shift to the right of the dose-response curve of noradrenaline, while the alpha(2)-antagonist, rauwolscine had no effect on the response to noradrenaline. Phenylephrine-evoked contractions of corporal strips were significantly inhibited by the alpha(1)-adrenoceptor antagonist, prazosin. 4. Isoprenaline and salbutamol each relaxed precontracted corpus cavernosum preparations in a concentration-dependent manner; the isoprenaline effect was blocked by propranolol, practolol and butoxamine. The salbutamol effect was blocked by butoxamine. 5. These results suggest that presence of postjunctional alpha(1)-adrenoceptors in horse corpus cavernosum. There is also a heterogenous population of beta-adrenoceptors in this tissue, belonging to the beta(1) and beta(2) subtypes.

Adrenergic alpha-Agonists↗
PubMed2002

Modulatory effect of the adrenergic system upon fibroblast proliferation: participation of beta 3-adrenoceptors.

1. The beta3-adrenoceptor agonist ZD 7114, like the non-selective beta-adrenoceptor agonist isoprenaline, but unlike the beta1-adrenoceptor agonist dobutamine and the beta2-adrenoceptor agonist salbutamol, produced an increment on mouse embryonic fibroblast proliferation. The half-maximal stimulation of cell growth occurred at substantially lower concentrations with the beta3-adrenoceptor agonist (EC50: 5.5 x 10(-8) m) than with isoprenaline (EC50: 1.25 x 10(-6) m). 2. The selective beta3-adrenoceptor antagonist SR 5923 OA prevented the beta3-stimulated fibroblast proliferation. Conversely, practolol and butoxamine did not prevent fibroblast growth. 3. Additionally, a decrease of cAMP was obtained in fibroblasts cells upon stimulation with isoprenaline and ZD 7114. 4. The expression of beta-adrenoreceptors on fibroblast cells was also studied by radioligand binding. The Ki values in the presence of beta1- and beta2-adrenoceptor antagonist was two-fold higher than the Ki values for beta3 adrenoceptor antagonist indicating the presence of A3-receptor subtype. 5. Inhibitors of different intracellular coupling pathways including phospholipase C (U 73122), protein kinase C (staurosporine), calcium/calmodulin (trifluoroperazine) and calcium channel (verapamil), prevented the stimulatory actions of the selective beta3-adrenoceptor agonist ZD 7114. 6. The presence of beta3-adrenoceptors on embryonic mouse fibroblast cells may play a role in the modulation of cell growth and biologic activity. The mechanism by which ZD 7114 triggers cell proliferation and function, involves the activation of phospholipase C, PKC, calcium/calmodulin and the influx of calcium.

Adrenergic Agonists↗
PubMed2002

From toxic precursors to safe drugs. Mechanisms and relevance of idiosyncratic drug reactions.

In adverse drug reactions, effects accounted for by the pharmacological profile of the drug may be distinguished from sometimes bizarre, unpredictable events ("idiosyncrasies"). In the majority of cases, the latter are due to reactive intermediates formed by members of the cytochrome P450 family of enzymes. These products are usually formed at very low quantities. However, genetic disposition (e.g. by enhanced expression of the catalyzing enzyme or failure of protective factors such as glutathione) or certain external conditions (for example comedication of inducers of drug metabolism) may lead to toxic intermediates being available at relevant quantities. Once generated, these metabolites will react with macromolecules and finally cause cell necrosis. Necrosis may result from direct damage to functions essential to the cell or be secondary to harmful immune reactions activated by recognition of the new structures as neoantigens. As the principal site of drug metabolism, the liver is most frequently affected by idiosyncratic reactions, which often enough are recognized only after large numbers of patients have been treated. The idiosyncratic potential of a drug relates to its chemical structure rather than its pharmacological mechanism. Risks are evident if biotransformation yields products with chemical substructures such as quinones, phenoles, acyl halides, aromatic and hydroxyl amines. There are numerous cases of precursor drugs with idiosyncratic potential that have been replaced or marginalized by agents with more favorable chemical properties. Examples include beta 1-preferential beta-adrenoceptor antagonists (toxic precursor: practolol) and the choline esterase inhibitors used in treatment of Alzheimer's disease. In the latter group, tacrine (CAS 321-64-2) gives rise to high liver enzyme levels in about 30% of the patients, an effect not shared with more recent, chemically different entities. A similar case can be made for the insulin sensitizer troglitazone (CAS 97322-87-7) (marketed, now withdrawn in the USA) and its successors rosiglitazone (CAS 122320-73-4) and pioglitazone (CAS 111025-46-8). Due to its different chemical structure, only troglitazone can be transformed into a reactive quinone metabolite, a process that may be accelerated by the drug inducing its own metabolism. In agreement with this view, there is no evidence of specific hepatic toxicity with the two successor drugs. Ongoing progress in molecular toxicology may aid in minimizing idiosyncratic hazards already at early stages of drug development.

Biotransformation↗
PubMed1983

Direct stimulation of beta 2-adrenergic receptors in rat anterior pituitary induces the release of adrenocorticotropin in vivo.

Previous work in our laboratory has shown that stimulation of beta 2-adrenergic receptors on mouse anterior pituitary tumor cells causes the secretion of immunoreactive adrenocorticotropin (ACTH). The present study was designed to test the hypothesis that catecholamines can cause the release of ACTH in vivo by the direct stimulation of beta 2-adrenergic receptors in the rat anterior pituitary. Systemic administration of a beta-adrenergic receptor agonist (-)-isoproterenol resulted in an increase in plasma ACTH levels in intact animals and in rats with transected pituitary stalks. This effect could be blocked by the beta-adrenergic receptor antagonist, propranolol, but not by the specific beta 1-adrenergic receptor antagonist, practolol. Salmefamol, a beta 2-adrenergic receptor agonist also elevated plasma ACTH levels in stalk-sectioned animals. Dexamethasone, a glucocorticoid that inhibits the synthesis and release of ACTH from the anterior pituitary but not the intermediate lobe, prevented the elevation of ACTH secretion by (-)-isoproterenol in stalk-transected rats. These data indicate that beta 2-adrenergic receptors are present on anterior pituitary cells and suggest that catecholamines can directly stimulate ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1988

High blood pressure induced by audiovisual stimulation in young rats: effect of antihypertensive agents.

High systolic blood pressure (BP) was induced in young Wistar rats by daily exposure for 30 mins to environmental stimuli consisting of intense (100 dB) sound of 7500 cps and flashing light (0.3 cps). Maximal BP enhancement was obtained after the application of both these stimuli for 3 consecutive days. Such a hypertensive response was detected 24 hrs, but not 1 hr after the trial. High BP backed to normal 72 hrs after discontinuation of the audiovisual stimulation trials. Clinically effective antihypertensive agents (clonidine, prazosin, propranolol, practolol and metoprolol) as well as a new compound under investigation (cicletanine) were proved active in this model. Normotensive nonstressed rats run in parallel did not show any variation in their BP after administration of the same dose of the drugs assayed. This experimental model of hypertension may be a useful tool not only to test new antihypertensive agents but also to study the intriguing question of the role of stress in the development and maintenance of essential hypertension.

Acoustic Stimulation↗
PubMed1977

Adrenergic mechanisms in infection. III. alpha-and beta-receptor blocking agents in treatment.

Raised epinephrine concentrations concentrations developed in the blood of mice near death after an intraperitoneal challenge with 10(9) Staphylococcus aureus or Escherichia coli. Both epinephrine levels were elevated in the urine near death. These challenges were infections and not intoxications, as they could be successfully treated with antibiotics. Using the same model infections, we studied the effect of alpha-and beta-receptor blocking agents and other adrenergically active compounds. The compounds alone were not toxic in the doses used. alpha-Blockers, such as phenoxybenzamine, dibenamine, and ergotamine and beta-blockers, such as butoxamine, timolol, and practolol, were ineffective. Phentolamine alone or propranolol alone showed some evidence of an ability to prolong life in S. aureus infections. Together they lengthened life significantly in S. aureus-challenged mice. In E. coli infections this beneficial effect was not noted. Mice pretreated with reserpine (7 mg/kg) and challenged with S. aureus lived 55% longer than saline-treated controls. Less benefit was noted in E. coli infections. Serontonin treatment was helpful in S. aureus infections and deleterious in E. coli infections.

Adrenergic alpha-Antagonists↗
PubMed2003

Improvement of peak shape and separation performance of beta-blockers in conventional reversed-phase columns using solvent modifiers.

A comparative study of peak shape, elution behavior, and resolution of 16 beta-blockers (acebutolol, alprenolol, atenolol, bisoprolol, carteolol, celiprolol, esmolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol, practolol, propranolol, sotalol, and timolol) chromatographed with hybrid mobile phases of triethylamine (TEA)-acetonitrile and sodium dodecyl sulfate (SDS)-propanol is performed using conventional reversed-phase columns and isocratic elution. Both solvent modifiers (TEA and SDS) prevent the interaction of the basic drugs with the alkyl-bonded phase. However, the protection mechanisms of silanols on the packing are different. Whereas TEA associates with the silanol sites (blocking ion-exchange processes or repelling the solutes), the long hydrophobic chain of SDS is inserted in the bonded organic layer with the sulfate group protruding outside, which makes the stationary phase negatively charged. The effects of TEA, acetonitrile, SDS, and propanol on the elution strength, efficiency, peak asymmetry, and resolution are examined under an experimental design basis that is assisted by computer simulation to reach more general conclusions. The combination of improved peak shapes, larger selectivity, and a smaller range in retention among compounds of extreme polarity leads to the observation that a greater number of beta-blockers can be resolved with a hybrid micellar system.

Adrenergic beta-Antagonists↗
PubMed2006

Experiences with carrier-mediated transport in liquid-phase microextraction.

Different organic borates, phosphates, sulphates, and carboxylic acids are evaluated as extraction carriers in three-phase liquid-phase microextraction (LPME). Hydrophilic basic drugs form ion-pairs with the carriers and are extracted as ion-pair complexes into an organic liquid membrane of n-octanol or peppermint oil immobilized in the pores of a polypropylene hollow fiber. From this point, the basic drugs are released into a 20-microL solution of 50mM HCl placed inside the lumen of the hollow fiber (acceptor solution). Simultaneously, the carrier is neutralized by protons from the acceptor solution (protonated to maintain the charge balance). Both water-soluble and water-insoluble carriers are tested. One promising candidate among the water-soluble carriers is 1-heptanesulfonic acid. This is added to the sample solution to a final concentration of 25mM and served to ion-pair the analytes within the sample solution. Among the less water-soluble candidates, a mixture of di(2-ethylhexyl) phosphate (DEHP) and tris(2-ethylhexyl) phosphate (TEHP) serve as efficient carriers. Ten percent (w/w) of each of DEHP and TEHP are added to the organic liquid membrane, and these carriers principally worked through ion-pairing with the analytes at the interface between the sample solution and the organic liquid membrane. Several carriers are found to be compatible with human plasma samples, and bromthymol blue is particularly efficient in combination with these protein-containing matrices. Following optimization of the conditions for bromthymol blue, including saturation of the plasma samples with sodium sulphate, extraction recoveries between 45% and 75% are obtained for eight model drugs after 60 min of extraction. With bromthymol blue as the carrier, highly acceptable validation data are obtained for phenylpropanolamine and practolol extracted from human plasma.

Anions↗
PubMed1991

New therapeutic strategies in chronic heart failure: challenge of long-term beta-blockade.

It is claimed that long-term treatment with beta-blockers improves cardiac function and exercise capacity in patients with various forms of congestive heart failure. This was first reported by Waagstein and coworkers in patients with idiopathic dilated cardiomyopathy in 1975 and was later confirmed in 8 further studies in this type of patient. A total of 211 patients with idiopathic dilated cardiomyopathy were treated for 12-19 months. About two thirds of the patients have improved to some extent. Seven other studies reported favourable long-term effects of beta-blockers in 120 patients with other forms of dilated cardiomyopathy, e.g. caused by coronary artery disease, adriamycin, diabetes, or valvular heart disease. Pooled data from 10 studies on 153 patients with various forms of cardiomyopathy, showed that ejection fraction was improved by 40% from 27 to 38%. Only two studies were inconclusive, both with only one month's treatment. In all studies with favourable effects of long-term beta-blockade, treatment was given for more than 2 months and in most cases for about 6 months. A number of beta-blockers have been used in the studies, including acebutulol, alprenolol, bucindolol, labetalol, metoprolol, practolol and propranolol. In most cases, a rather low dose was given initially and there was a stepwise increase in the dosages. After 6-8 weeks most patients were given beta-blockers in daily doses comparable to those given in patients with angina pectoris and hypertension. There is at present no indication that one beta-blocker is superior to others. It therefore seems reasonable to believe that the effects are due to beta 1-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1983

Haemodynamic consequences of intrinsic sympathomimetic activity and cardioselectivity in beta-blocker therapy for hypertension.

The relevance of intrinsic sympathomimetic activity (ISA) and cardioselectivity for the acute and long-term haemodynamic effects of beta-blocker therapy for hypertension was assessed from reports in the literature. The beta-blockers included in this survey are pindolol, practolol, alprenolol, oxprenolol, acebutolol, penbutolol, metoprolol, atenolol, propranolol and timolol. Forty-four acute and 41 long-term studies in 430 and 482 subjects respectively, were analysed. In acute studies arterial pressure is barely lowered, whereas in spite of the many pharmacological and physicochemical differences beta-blockers appear to have a hypotensive effect of approximately equal magnitude during long-term treatment. In the acute studies, the falls in heart rate, stroke volume, cardiac output and subsequently increased total peripheral resistance are inversely proportional to the pharmacologically defined quantity of ISA of the beta-blockers. The response of vascular resistance to cardiodepression is similar for non-selective and beta 1-selective agents. During long-term therapy, the inverse correlation between cardiac output and vascular resistance is shifted to a lower level of vascular resistance. This reduction of vascular resistance at any level of cardiac output that underlies the hypotensive action of beta-blockers is associated with an increase in stroke volume. Thus, the absolute value of vascular resistance during beta-blocker therapy is determined by the degree of ISA, irrespective of the quality of cardioselectivity. Consequently, beta-blockers with sufficient ISA to prevent disturbance of tissue perfusion at rest reduce the characteristically elevated vascular resistance in longstanding arterial hypertension in contrast with beta-blockers lacking this property. This can have implications for the long-term prognosis of this condition.

Adrenergic beta-Antagonists↗
PubMed1995

Assessing the safety profile of a new antihypertensive agent.

GUIDELINES ON DRUG SAFETY: Recent European Union draft guidelines for the safety evaluation of drugs intended for long-term use state that during drug development the safety profile of the new compound should be assessed over a period of time consistent with intended usage. This is in reasonable agreement with guidelines prepared by other regulatory authorities. CLINICAL DRUG DEVELOPMENT: Satisfactory preclinical data on a new compound are used to obtain authorization for human testing from the National Committees on Safety of Medicines. Clinical trials are performed in four phases, ranging from phase I studies performed on healthy volunteers (n = 20-50) to postmarketing (phase IV) studies. The latter are of great importance as they cover large patient populations (n = 2000 to > or = 10,000) and allow detection of rare adverse drug reactions. ADVERSE DRUG REACTIONS: Type B reactions are serious, unpredictable reactions to a drug that necessitate treatment withdrawal. Type A reactions are dose-dependent, and represent the majority of adverse reactions. They are often managed by dose reduction rather than drug withdrawal. ADVERSE REACTIONS TO ANTIHYPERTENSIVE AGENTS: Examples of type B adverse reactions to antihypertensives are the cutaneous and ocular reactions to practolol, and angioneurotic oedema associated with angiotensin converting enzyme inhibitors. Lacidipine, a second-generation calcium antagonist, is an example of a modern antihypertensive agent with a favourable safety profile. The adverse reactions associated with lacidipine are mild to moderate and of the A type, the major ones being those typical of calcium antagonists (headache, flushing and pedal oedema due to vasodilation.

Antihypertensive Agents↗
PubMedDate not supplied

Coexistence of beta 1- and beta 2-adrenoceptors in the rabbit heart: quantitative analysis of the regional distribution by (-)-3H-dihydroalprenolol binding.

We determined the amount of beta 1- and beta 2-adrenoceptors in right and left atria and ventricles of rabbits. For this purpose inhibition of specific (-)-3H-dihydroalprenolol [(-)-3H-DHA] binding (5 nM) by beta 1-selective (practolol, metoprolol) and beta 2-selective (zinterol, IPS 339) adrenergic drugs was determined and analyzed by pseudo-Scatchard (Hofstee) plots. For both atria, inhibition of binding by the four selective beta-adrenergic drugs resulted in non-linear Hofstee plots, suggesting the coexistence of both beta-adrenoceptor subtypes. From these plots we calculated a beta 1:beta 2-adrenoceptor ratio of 72:28 for the right atrium and of 82:18 for the left. In contrast, only a very small amount of beta 2-adrenoceptors (approximately 5-7% of the total beta-adrenoceptor population) could be detected in the ventricles. For comparison we analyzed the inhibition of specific (-)-3H-DHA binding in tissues with homogeneous population of beta-adrenoceptors (beta 1:guinea pig left ventricle; beta 2: cerebellum of mature rats). For both tissues the four selective beta-adrenergic drugs showed linear Hofstee plots, demonstrating that in tissues with homogeneous beta-receptor population interaction of each drug with the receptor followed simple mass-action kinetics. We conclude that beta 1- and beta 2-adrenoceptors coexist in rabbit atria while the ventricles are predominantly endowed the beta 1-adrenoceptors.

Alprenolol↗
PubMedDate not supplied

Vasodilation by medroxalol mediated by beta 2-adrenergic receptor stimulation.

A contribution by active vasodilation to the hypotensive effect of medroxalol was investigated in anesthetized dogs and reserpinized pithed rats. In anesthetized dogs, intravenous doses of medroxalol, which decreased blood pressure and heart rate, also produced a dose-related vasodilation in the isolated perfused gracilis muscle in situ. This vasodilator effect of medroxalol was completely blocked by propranolol; the hypotensive effect of medroxalol was inhibited 50% by propranolol but not at all by practolol. In reserpinized pithed rats with angiotensin-supported blood pressure, intravenous doses of medroxalol also produced propranolol-sensitive decreases in diastolic blood pressure and did not alter heart rate. Labetalol produced similar effects but was significantly less potent. Comparatively, equivalent amounts of isoproterenol and pindolol decreased diastolic blood pressure but increased heart rate. In the isolated guinea pig trachea, medroxalol produced a propranolol-sensitive relaxation at concentrations that antagonized the relaxant effects of salbutamol. Identical concentrations of medroxalol did not increase rate of isolated guinea pig atria. It is concluded that a substantial portion of the hypotensive effect of medroxalol is due to a beta 2-adrenergic-receptor-mediated vasodilation.

Adrenalectomy↗