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Biomedical subjects

O E Brodde

Publications and source records attributed to O E Brodde.

At least 145 records · Page 8Linked to original sources
PubMed1988

Are alpha- and beta-adrenoceptor changes in patients with essential hypertension genetically determined?

In order to find out whether adrenoceptor changes in essential hypertension might be genetically determined, we measured platelet alpha 2- and lymphocyte beta 2-adrenoceptor density in 48 normotensive children with normotensive parents, and 41 normotensive children who had one essential hypertensive parent and thus should have had a genetic predisposition for the development of hypertension. The groups did not differ with regard to blood pressure and heart rate, age, body weight and height, plasma renin activity and catecholamines, and serum electrolytes and creatinine. Lymphocyte beta 2-adrenoceptor density (assessed by 125I-iodocyanopindolol binding) and responsiveness (assessed as 10 mumol/l isoprenaline-induced cyclic AMP increases) did not differ between the groups. Platelet alpha 2-adrenoceptor density (assessed by 3H-yohimbine binding) was significantly higher in children with one essential hypertensive parent. We conclude that platelet alpha 2- but not lymphocyte beta 2-adrenoceptor changes in essential hypertension are genetically determined.

Blood Platelets↗
PubMed1988

Selective regulation of beta 1- and beta 2-adrenoceptors in the human heart by chronic beta-adrenoceptor antagonist treatment.

1. In 44 patients undergoing coronary artery bypass grafting, the effect of chronic administration of the beta-adrenoceptor antagonists sotalol, propranolol, pindolol, metoprolol and atenolol on beta-adrenoceptor density in right atria (containing 70% beta 1- and 30% beta 2-adrenoceptors) and in lymphocytes (having only beta 2-adrenoceptors) was studied. 2. beta-Adrenoceptor density in right atrial membranes and in intact lymphocytes was assessed by (-)-[125I]-iodocyanopindolol (ICYP) binding; the relative amount of right atrial beta 1- and beta 2-adrenoceptors was determined by inhibition of ICYP binding by the selective beta 2-adrenoceptor antagonist ICI 118,551 and analysis of the resulting competition curves by the iterative curve fitting programme LIGAND. 3. With the exception of pindolol, all beta-adrenoceptor antagonists increased right atrial beta-adrenoceptor density compared to that observed in atria from patients not treated with beta-adrenoceptor antagonists. 4. All beta-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor density; on the other hand, only sotalol and propranolol also increased right atrial beta 2-adrenoceptor density, whereas metoprolol and atenolol did not affect it and pindolol decreased it. 5. Similarly, in corresponding lymphocytes, only sotalol or propranolol increased beta 2-adrenoceptor density, while metoprolol and atenolol did not affect it and pindolol decreased it. 6. It is concluded that beta-adrenoceptor antagonists subtype-selectively regulate cardiac and lymphocyte beta-adrenoceptor subtypes. The selective increase in cardiac beta 1-adrenoceptor density evoked by metoprolol and atenolol may be one of the reasons for the beneficial effects observed in patients with end-stage congestive cardiomyopathy following intermittent treatment with low doses of selective beta 1-adrenoceptor antagonists.

Adrenergic beta-Antagonists↗
PubMed1988

Differentiation of beta 1- and beta 2-adrenoceptor-mediated effects in humans.

To differentiate beta 1- and beta 2-adrenoceptor-mediated effects in humans, we studied the effects of a 2-wk treatment of 12 male volunteers with the selective beta 1-adrenoceptor antagonist bisoprolol (1 x 10 mg/day) and the beta 2-selective antagonist ICI 118,551 (3 x 25 mg/day) on lymphocyte beta 2-adrenoceptor density and responsiveness [10 microM l-isoproterenol (IPN) evoked adenosine 3',5'-cyclic monophosphate (cAMP) increase] as well as on exercise- and IPN-induced changes in lymphocyte beta 2-adrenoceptor density, blood pressure, heart rate, and plasma norepinephrine levels. ICI 118,551 administration increased lymphocyte beta 2-adrenoceptor density and responsiveness by approximately 50%, whereas bisoprolol had no effect. Dynamic exercise on a bicycle and infusion of graded doses of IPN led to an approximately 100% increase in lymphocyte beta 2-adrenoceptor density; this was abolished by ICI 118,551 but not affected by bisoprolol. ICI 118,551 markedly attenuated IPN-induced decrease in diastolic blood pressure but did not affect increase in systolic blood pressure, whereas bisoprolol had opposite effects. The IPN-induced increase in heart rate, however, was antagonized by both bisoprolol and (to a greater extent) ICI 118,551. Finally, ICI 118,551 completely abolished the IPN-induced increase in plasma norepinephrine levels, whereas bisoprolol had no effect. These results indicate that bisoprolol and ICI 118,551 are suitable tools to differentiate in humans beta 1- and beta 2-adrenoceptor-mediated effects.

Adult↗
PubMed1988

Beta-adrenoceptor changes in hypertension: cause or consequence of the elevation in blood pressure?

Cardiac, pulmonary and renal beta-adrenoceptor density and subtype distribution were measured by radioligand binding in three rat models of acquired hypertension. Dahl salt-sensitive (DS) rats on a high-sodium diet, renal hypertensive rats and DOCA-salt rats. The results were compared with previously obtained data from spontaneously hypertensive rats (SHR) of different ages and from SHR treated with the immunosuppressant cyclosporin A. Cardiac and pulmonary beta-adrenoceptor density and subtype distribution were unaltered in any of the three groups compared with their respective controls. However, renal beta-adrenoceptor density was uniformly increased without alterations of the beta 1: beta 2-adrenoceptor ratio. The previously described beta 2-adrenoceptor increase in heart and lung of SHR was not found in any model of acquired hypertension and might be characteristic for the SHR. However, renal beta-adrenoceptor alterations seem generally to occur secondary to blood pressure elevation.

Animals↗
PubMed1987

Alpha-adrenoceptor antagonistic action of amiloride.

1. In isolated perfused rat liver, the effects of alpha-adrenergic stimulation by phenylephrine (2 microM), such as an increase of portal pressure, glucose output, Ca2+ release into the perfusate and the characteristic K+ flux changes across the hepatocyte plasma membrane were almost completely abolished in the presence of amiloride (0.5 mM). 2. When the phenylephrine concentration was raised to about 100 microM, the effects of the alpha-adrenergic agonist on hepatic metabolism, Ca2+ and K+ fluxes, but not on the portal venous pressure, were restored, suggesting a competitive antagonism by amiloride. 3. Amiloride antagonized in a concentration-dependent manner noradrenaline-induced isometric contractions of strips of the rabbit pulmonary artery. The concentration-response curve of noradrenaline was shifted to the right, and the maximal response obtained was also depressed, suggesting a mixed competitive and non-competitive antagonism. The estimated amiloride-adrenoceptor-dissociation constant was 8 microM. 4. The affinity of amiloride to the alpha- and beta-adrenoceptor subtypes was determined by radioligand binding assays using [125I]BE 2254 binding to rat liver plasma membranes (alpha 1-subtype), [3H]yohimbine binding to human platelet membranes (alpha 2-subtype), (-)-[125I]iodocyanopindolol (ICYP) binding to rabbit lung membranes in presence of the beta 2-adrenoceptor antagonist ICI 118,551 (beta 1-subtype) and ICYP binding to rat lung membranes in presence of the beta 1-blocker atenolol (beta 2-subtype). In all systems, amiloride inhibited specific ligand binding concentration-dependently, the Ki values for amiloride were about 25, 52, 148 and 161 microM for alpha 1- alpha 2-, beta 1- and beta 2-adrenoceptor subtypes, respectively. 5. It is concluded that amiloride in concentrations below those required for inhibition of the Na+/H+ exchanger is a potent antagonist of alpha- and beta-adrenoceptors in a variety of experimental systems. Whether the adrenergic antagonism of amiloride is important for antihypertensive therapy, remains to be elucidated.

Adrenergic alpha-Antagonists↗
PubMed1987

The role of cyclic AMP in the positive inotropic effect mediated by beta 1- and beta 2-adrenoceptors in isolated human right atrium.

The time course of the effects of isoprenaline (3 X 10(-7) mol/l) on contractile force and on the cyclic AMP level was studied in the electrically driven isolated muscle strip of the human right atrium. Isoprenaline produced a rise in cyclic AMP content (maximum increase after 60 s) preceding the increase in contractile force. The effects of isoprenaline on contractile force and on the intracellular level of cyclic AMP were enhanced in the presence of the phosphodiesterase inhibitor papaverine (10(-5) mol/l). On the other hand, the beta-adrenoceptor antagonist propranolol (10(-7) mol/l) suppressed isoprenaline-induced cyclic AMP increases, but reduced the increase in force of contraction by only 35%. In addition, both the beta 1-selective antagonist bisoprolol (3 X 10(-9)-3 X 10(-8) mol/l) and the beta 2-selective antagonist ICI 118,551 (3 X 10(-9)-3 X 10(-8) mol/l) inhibited the isoprenaline-induced cyclic AMP increase concentration-dependently; ICI 118,551 produced more pronounced inhibition than bisoprolol. It is concluded that cyclic AMP is involved in the positive inotropic action of isoprenaline evoked by beta 1- and beta 2-adrenoceptor stimulation in isolated human right atrium; however, an additional cyclic AMP independent mechanism cannot be ruled out.

Adrenergic beta-Antagonists↗
PubMed1987

Dynamic exercise-induced increase in lymphocyte beta-2-adrenoceptors: abnormality in essential hypertension and its correction by antihypertensives.

We compared the effects of acute stimulation of sympathetic activity by dynamic exercise on a bicycle on lymphocyte beta 2-adrenoceptor density and 10 mumol/L (-)-isoprenaline-evoked lymphocyte cyclic adenosine monophosphate increases in normotensive volunteers with those in patients with essential hypertension. In normotensive subjects exercise increased lymphocyte beta 2-adrenoceptors by about 100%. This effect seems to be a beta 2-dependent process, since it is prevented by propranolol (5 mg administered intravenously) and the beta 2-selective antagonist ICI 118,551 (25 mg t.i.d. orally for 2 weeks) but not by the beta 1-selective antagonist bisoprolol (2.5 mg administered intravenously). In patients with essential hypertension who have elevated lymphocyte beta 2-adrenoceptors, dynamic exercise caused only marginal beta 2-adrenoceptor changes, suggesting an impairment of the acute beta-adrenoceptor regulation. Normalization of blood pressure by antihypertensive treatment resulted in a significant fall in lymphocyte beta 2-adrenoceptors and in a restoration of exercise-induced beta 2-adrenoceptor increases. It is concluded that in essential hypertension the impairment of beta-adrenoceptor regulation is directly linked to the elevated blood pressure.

Adult↗
PubMed1987

Arterial hypotension in chronic hemodialyzed patients.

We studied in 32 patients on maintenance hemodialysis (duration of treatment 6 to 133 months) whether duration of dialysis treatment affects blood pressure, plasma noradrenaline levels and alpha 2-adrenoceptor density (assessed in platelet membranes by 3H-yohimbine binding). Plasma noradrenaline levels were a significant inverse correlation to platelet alpha 2-adrenoceptor density. In addition, mean arterial blood-pressure, plasma noradrenaline levels and platelet alpha 2-adrenoceptor density were significantly related to the duration of treatment: with increasing duration of treatment plasma noradrenaline levels increased, whereas mean arterial blood-pressure and platelet alpha 2-adrenoceptor density decreased. Furthermore, changes in mean arterial blood-pressure were inversely related to plasma noradrenaline levels and positively to platelet alpha 2-adrenoceptor density. Platelet alpha 2-adrenoceptor changes were accompanied by similar alterations in (vascular) alpha 1-adrenoceptor responsiveness (assessed by blood pressure responses to i.v. injections of phenylephrine); in hypotensive hemodialysis patients, who had high, plasma noradrenaline levels and low, platelet alpha 2-adrenoceptor density, the dose of phenylephrine necessary to increase systolic blood pressure by 20 mm Hg was nearly twice as high as in normotensive dialysis patients and healthy controls. In autonomic tests, Valsalva-ratio was lower in hypotensive than in normotensive dialysis patients and healthy controls, whereas no differences were found in blood pressure and heart rate responses during sustained hand-grip exercise as well as in beat-to-beat variation during deep breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Increased beta 2-adrenoreceptor density in heart, kidney and lung of spontaneously hypertensive rats.

The development of beta-adrenoreceptor density and beta 1- and beta 2-adrenoreceptor distribution has been investigated in heart, kidney and lung of spontaneously hypertensive (SHR) and normotensive (WKY) rats by (-)125I-iodocyanopinolol binding at the age of 5-6, 9-10 and 19-21 weeks. At all ages beta-adrenoreceptor density was similar in hearts of both strains, while it was increased in kidney and lung of SHR compared to WKY. The beta 2-adrenoreceptor density was higher in all three tissues of SHR at all ages investigated. On the other hand, beta 1-adrenoreceptor density was decreased in heart, unchanged in lung and increased in kidney of SHR compared to WKY. Destruction of presynaptic nerve terminals by treatment of WKY with 6-hydroxydopamine produced a 24% loss of cardiac beta 2-adrenoreceptors, whereas the beta 1-adrenoreceptor density remained unchanged, suggesting that at least part of the cardiac beta 2-adrenoreceptor population is localized prejunctionally. It is suggested that beta 2-adrenoreceptors are involved in the development or maintenance of high blood pressure in SHR, possibly by facilitating noradrenaline release.

Animals↗
PubMed1987

Beta-2 adrenoceptor-mediated relaxation of the isolated human saphenous vein.

On isolated strips of human saphenous vein, pretreated with 5 microM phenoxybenzamine and contracted with 10 mM KCl, the beta adrenoceptor mediating the relaxant effects of isoproterenol, procaterol and norepinephrine was characterized using the selective beta-1 adrenoceptor antagonist, bisoprolol, and the selective beta-2 adrenoceptor antagonist, ICI 118,551. All three agonists produced concentration-dependent relaxations of the isolated saphenous vein with an order of potency: procaterol (pD2 value, 7.69) greater than isoproterenol (pD2 value, 7.41) much greater than norepinephrine (pD2 value, 5.30). ICI 118,551 (3 X 10(-10) to 3 X 10(-9) M) was nearly 100 times more potent than bisoprolol (10(-7) to 10(-6) M) in antagonizing the relaxant effects of isoproterenol and procaterol. The slopes of the Schild plots for the antagonistic effects of ICI 118,551 and bisoprolol against isoproterenol- and procaterol-induced relaxations were not significantly different from unity indicating interaction with a homogeneous population of beta adrenoceptors. The pA2 value for ICI 118,551 amounted to 9.11 to 9.20 and for bisoprolol to 6.50 to 6.63. In addition, the concentration-response curve for the relaxant effect of norepinephrine was significantly shifted to the right by 10(-9) M ICI 118,551, but not affected by 10(-7) M bisoprolol. These results indicate that on the isolated strips of the human saphenous vein the beta adrenoceptor mediating relaxation is of the beta-2 subtype.

Bisoprolol↗
PubMed1986

Human beta-adrenoceptors: relation of myocardial and lymphocyte beta-adrenoceptor density.

In human right atria obtained from 21 patients during open-heart surgery, beta-adrenoceptor density [assessed by iodine-125-labeled (-)-cyanopindolol binding] and responsiveness (positive inotropic responses to isoprenaline) were linearly related to the beta-adrenoceptor density in the corresponding circulating lymphocytes. This direct relation of human myocardial and lymphocyte beta-adrenoceptor alterations, therefore, makes it possible to monitor drug- or disease-induced beta-adrenoceptor changes in tissues not easily accessible in humans.

Female↗
PubMed1986

Beta-adrenoceptor antagonists (non-selective as well as beta 1-selective) with partial agonistic activity decrease beta 2-adrenoceptor density in human lymphocytes. Evidence for a beta 2-agonistic component of the partial agonistic activity.

In the present study the effects of pindolol [non-selective beta-adrenoceptor antagonist with strong partial agonistic activity (PAA)] on beta 2-adrenoceptor density in lymphocytes (assessed by (-)-[125I]iodocyanopindolol (ICYP) binding) were compared with those of the beta 1-selective antagonists celiprolol (with PAA) and bisoprolol (no PAA) in normotensive young volunteers to get further insights into the nature of PAA. Administration of pindolol (2 X 5 mg/day) caused an about 25% decrease in lymphocyte beta 2-adrenoceptor density after 2 days; during treatment beta 2-adrenoceptor density declined further (maximum decrease after 7 days: 50%). After withdrawal of pindolol lymphocyte beta 2-adrenoceptor density recovered very slowly being still after 4 days significantly reduced, although no pindolol was detectable in plasma after 36 h. The KD-values for ICYP, however, did not change during or after pindolol treatment. The decrease in lymphocyte beta 2-adrenoceptor density induced by pindolol could be completely prevented by simultaneous administration of propranolol (3 X 40 mg/day) indicating that the PAA of pindolol is the cause of its beta-adrenoceptor decreasing effect. Administration of the non-selective beta-adrenoceptor antagonist bopindolol (1 X 2 mg/day) with PAA caused decreases in lymphocyte beta 2-adrenoceptor density (maximum decrease after 7 days: 40%); concomitantly the 10 mumol/l (-)-isoprenaline evoked increases in the intracellular level of lymphocyte cyclic AMP were attenuated to a similar extent indicating that the beta-adrenoceptor antagonist-induced decrease in beta-adrenoceptor density is accompanied by a loss in beta-adrenoceptor function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1986

Human myocardial beta-adrenoceptors: demonstration of both beta 1- and beta 2-adrenoceptors mediating contractile responses to beta-agonists on the isolated right atrium.

On the isolated electrically driven muscle strip of human right atrial appendages the beta-adrenoceptor subtypes mediating the positive inotropic effects of isoprenaline, dobutamine and procaterol were characterized using the beta 1-selective antagonist bisoprolol and the beta 2-selective antagonist ICI 118,551. The three agonists induced concentration-dependent increases in force of contraction with an order of potency: procaterol (pD2-value: 8.03) greater than isoprenaline (pD2-value: 7.73) greater than dobutamine (pD2-value: 5.44). In saturating concentrations all three agonists produced the same maximum of developed tension. ICI 118,551 (10(-9)--10(-7) mol/l) and bisoprolol (10(-9)--10(-7) mol/l) were nearly equipotent in antagonizing the positive inotropic effects of isoprenaline and dobutamine. However, the slopes of the Schild-plots for both antagonists against both agonists were significantly less than 1.0 indicating interaction with beta 1- and beta 2-adrenoceptors. On the other hand, ICI 118,551 (10(-10)--10(-8) mol/l) was approximately 100 times more potent than bisoprolol (10(-8)--10(-6) mol/l) in antagonizing the positive inotropic effect of the highly selective beta 2-agonist procaterol. In addition, the slopes of the Schild-plots for antagonism of ICI 118,551 and bisoprolol against procaterol were not significantly different from unity indicating interaction with a homogeneous class of beta-adrenoceptors. The pA2-value for ICI 118,551 was 9.49, for bisoprolol it amounted to 6.99.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1986

Bisoprolol (EMD 33512), a highly selective beta 1-adrenoceptor antagonist: in vitro and in vivo studies.

The properties of the newly developed selective beta 1-adrenoceptor antagonist bisoprolol (EMD 33152) were investigated by in vitro and in vivo studies. Binding studies with (-)-[125I] iodocyanopindolol (ICYP) revealed that the affinity of (+/-)-bisoprolol to beta 1-adrenoceptors was approximately 100 times higher than to beta 2-adrenoceptors. This high beta 1-adrenoceptor selectivity of bisoprolol could be confirmed in binding studies with the tritiated compound (-)[3H] bisoprolol, which labelled in rabbit lung membranes--a tissue known to contain 80% beta 1- and 20% beta 2-adrenoceptors--exclusively beta 1-adrenoceptors. In physiological studies, (+/-)-bisoprolol was found to be devoid of any intrinsic sympathomimetic activity (ISA), since it had no positive chronotropic effects on spontaneously beating right atria of reserpinized rats. On isolated electrically driven human right atria, (+/-)-bisoprolol was approximately 30 times more potent in antagonizing the beta 1-adrenoceptor-mediated positive inotropic effect of noradrenaline (pA2-value, 8.42) than the beta 2-adrenoceptor-mediated positive inotropic effect of procaterol (pA2-value, 6.99). To test the beta 1-adrenoceptor selectivity in vivo, the effects of bisoprolol administration (1 X 10 mg/day for 9 days) on lymphocyte beta 2-adrenoceptor density [assessed by (-)-ICYP binding] in healthy volunteers were compared with those of the nonselective beta-adrenoceptor antagonists propranolol (4 X 40 mg/day for 9 days) without ISA, and pindolol (2 X 5 mg/day for 9 days) with ISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1986

Molecular pharmacology of beta-adrenoceptors.

The development of radioligand-binding studies has greatly advanced our knowledge of the molecular pharmacology of beta-adrenoceptors. With this technique it is possible for the first time to directly determine the tissue concentration of beta-adrenoceptors, and by this, the responsiveness of tissues to beta-adrenergic stimulation. One major insight into the molecular pharmacology of beta-adrenoceptors to come from radioligand-binding studies was that the tissue concentration of beta-adrenoceptors is not a fixed number, but is rather dynamically regulated by a variety of drugs, hormones, physiological and pharmacological conditions. Since changes in beta-adrenoceptors assessed in circulating lymphocytes of man mirror changes in density and functional responsiveness of the corresponding myocardial beta-adrenoceptors, alterations in beta-adrenoceptor function can be also studied in human beings. In addition, by means of radioligand-binding studies the coexistence of beta 1- and beta 2-adrenoceptors has been demonstrated in numerous tissues of various species, including human heart and lung. The detailed knowledge of distribution and regulation of beta-adrenoceptors should help to improve the individual effectiveness of drug treatment.

Animals↗
PubMed1986

Effect of propranolol, alprenolol, pindolol, and bopindolol on beta 2-adrenoceptor density in human lymphocytes.

Abrupt withdrawal of beta-adrenoceptor antagonists may lead to "rebound effects." To investigate the position of the new nonselective beta-adrenoceptor antagonist bopindolol [with moderate intrinsic sympathomimetic activity (ISA)], this drug was compared with propranolol (no ISA), alprenolol (weak ISA), and pindolol (marked ISA). The effects on lymphocyte beta 2-adrenoceptor density--assessed by (+/-)-[125I]iodocyanopindolol (ICYP) binding--were investigated in healthy volunteers aged 23-35 years. None of the test drugs changed the affinity of ICYP for beta 2 adrenoceptors. Propranolol treatment (4 X 40 mg/day) increased the density of beta 2-adrenoceptors by 25% after 2 days; during treatment beta 2-adrenoceptor density remained elevated. After withdrawal of propranolol, beta 2-adrenoceptor density declined slowly, being still significantly increased after 3 days, although propranolol was not detectable in plasma after 24 h, though heart rate was significantly increased. Alprenolol treatment (4 X 100 mg/day) did not significantly affect beta 2-adrenoceptor density. Pindolol treatment (2 X 5 mg/day) caused a 50% decrease of beta 2-adrenoceptor density after 2 days, which remained reduced during treatment. After withdrawal, beta 2-adrenoceptor density was still significantly diminished after 4 days. During and after treatment heart rate was not affected. Bopindolol treatment (2 mg/day) caused a 40% decrease of beta 2-adrenoceptor density after 2 days, which remained reduced during treatment. After withdrawal, beta 2-adrenoceptor density was still significantly diminished after 4 days. During and after treatment heart rate was not affected. It is concluded that the ISA may play an important role in modulating beta 2-adrenoceptor density and hence tissue responsiveness to beta-adrenoceptor stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗