Beta-adrenoreceptor Density Research Articles

Mirsaid M. Mirrakhimov (1927–2008): memoriam tribute for the clinician, scientist, and teacher. An obituary dedicated on the occasion of his day of birth

Mirsaid M. Mirrakhimov was born in 27 March 1927 at Frunze, Soviet Union (currently Bishkek, Kyrgyzstan), into a family of well-known local musician and director of National Philharmonics. After graduating school with honors, he decided to study medicine, despite a talent in music and his father’s insistence to follow his path. He was the first ever member of his family to pursue medicine. After passing entrance examinations, he became a student of the Kyrgyz State Medical Institute (KSMI, currently Kyrgyz State Medical Academy), from which he graduated with distinction. Despite an invitation from a famous local surgeon to enter surgical residency, Mirsaid M. Mirrakhimov pursued the internal medicine pathway, in which he had a keen interest. He finished residency in 1952, and was recruited as assistant professor of medicine at the Department of Internal Medicine, and started his Ph.D. work. In 1966, he became a full professor and was elected as the chief of Internal Medicine Department of the KSMI. Following his initiative and efforts, the National Center of Cardiology and Internal Medicine (NCCIM) was founded in 1977 at Frunze—the first such center in the whole Central Asian region. Prof. Mirrakhimov served as director of NCCIM from its foundation until 2007. As a part of recognition of his outstanding contribution for medical science, he was elected as a full member of the Academy of Medical Sciences of the Soviet Union in 1988. In 2001 NCCIM was named after Prof. Mirrakhimov by the decision of the president of the Kyrgyz Republic. As a scientist, he proved to be an extraordinarily gifted and creative investigator. He developed a number of novel diagnostic and therapeutic methods for general and environmental cardiology, particularly in the field of the high altitude physiology, adaptation of subjects to high altitude, and high-altitude pulmonary hypertension (HAPH). Mirsaid Mirrakhimov and colleagues showed that people residing at high altitude have a lower chemoreceptor threshold for PaCO2 [1]. Another important finding by his research group was that patients with HAPH have lower density of betaadrenoreceptors compared to healthy people [2]. Another study entitled “New approaches to noninvasive assessment of pulmonary artery pressure,” published in the Clinical Cardiology in 1992, became a classic and pioneering A. E. Mirrakhimov (*) Kyrgyz State Medical Academy, Akhunbaev Street 92, Bishkek 720020, Kyrgyzstan e-mail: amirrakhimov1@gmail.com

Autonomic imbalance hypothesis and overtraining syndrome.

The parasympathetic, Addison type, overtraining syndrome represents the dominant modern type of this syndrome. Beside additional mechanisms, an autonomic or neuroendocrine imbalance is hypothesized as underlying. Several findings support this thesis. During heavy endurance training or overreaching periods, the majority of findings give evidence of a reduced adrenal responsiveness to ACTH. This is compensated by an increased pituitary ACTH release. In an early stage of the overtraining syndrome, despite increased pituitary ACTH release, the decreased adrenal responsiveness is no longer compensated. The cortisol response decreases. In an advanced stage of overtraining syndrome, the pituitary ACTH release also decreases. In this stage, there is additionally evidence for decreased intrinsic sympathetic activity and sensitivity of target organs to catecholamines. This is indicated by decreased catecholamine excretion during night rest, decreased beta-adrenoreceptor density, decreased beta-adrenoreceptor-mediated responses, and increased resting plasma norepinephrine levels and responses to exercise. However, this complete pattern is only observed subsequent to high-volume endurance overtraining at high caloric demands. The described functional alterations of pituitary-adrenal axis and sympathetic system can explain persistent performance incompetence in affected athletes.

Relation between beta-adrenergic receptor density and lymphocyte proliferation associated with acute stress

The relations between acute changes in beta-adrenoreceptor density on lymphocytes and lymphocyte proliferation to a laboratory speech stressor were examined. Male participants either prepared and delivered a challenging speech task or read from a list of words. Participants engaged in the speech task, but not those involved in reading, exhibited significant increases in systolic blood pressure (an index of sympathetic nervous system arousal) and beta-adrenoreceptor density, accompanied by significant decreases in lymphocyte proliferation to pokeweed mitogen (PWM) but not concanavalin A (Con A). Increases in adrenoreceptor density significantly predicted decreases in lymphocyte activity in response to both mitogens. The increases in beta-adrenoreceptor density in the speech task condition occurred within 5 min after the baseline period, when participants were preparing for the speech task, but not yet speaking. These findings suggest that an acute stressor eliciting sympathetic nervous system activity can evoke rapid changes in beta-adrenoreceptor activity and decreases in mitogenic responses.

Relation between lymphocyte β-adrenergic responsivity and the severity of depressive disorders

Basal level and isoproterenol-induced response of cyclic adenosine monophosphate (cAMP) were determined in mononuclear leucocytes from 17 drug-free patients with major depressive (n = 9) or dysthymic disorders (n = 8) and 20 normal controls. No significant difference was observed between basal cAMP levels from depressed and control subjects. The cAMP production in response to maximal stimulation by isoproterenol (ISO), a β-agonist, was significantly lower (−34.7%) in depressed patients than in controls, and was significantly negatively correlated to the severity of the depression as assessed by the Hamilton depression rating scale score (r = −0.62; p < 0.003). When the depressed group was subdivided on the basis of the DSM-III-R (APA 1987) diagnosis criteria into major depressive and dysthymic disorders, the ISO-stimulated cAMP levels in the two groups were indistinguishable. When evaluated at the same time than the density of beta-adrenoreceptors in eight depressed patients, the ISO-stimulated cAMP levels were highly significantly correlated with the B max values (r = 0.89; p < 0.003). The results indicate that the decrease in beta-adrenergic responsiveness of mononuclear leukocytes can be present in depressed patients whatever the nosographical subtype of the depressive disorder and is quantitatively related to the depression severity. Based on these data, it seems that the blunted beta-adrenergic sensitivity observed in mononuclear leukocytes (MNL) cells of depressed patients is closely associated with a loss of beta-adrenoceptors.

Beta-adrenoreceptor density and coupling to GS protein in PTSD

Beta-adrenoreceptor density and coupling to GS protein in PTSD

Higher beta adrenoreceptor density and supercoupling to G S protein in panic disorder

Coupling of BAR to G s protein and treatment effects have not been examined. Neutmphil BAR were measured in 34 normal controls (NC) and 27 PD patients and repeated in 10 imipramine-treated patients. BAR were assayed according to method of Davis & Lelkowitz (I 980). Receptor density in the highand Iow.conformational states (R u and Rt.) and the agonist affinity to these states (Ktl and Kt.) were measured using LIGAND. %R a and the K I/Ktt ratio were used as indices of BAR coupling ~0 Gs protein. Group differences and treatment effects were examined using independent t-tests. There was no difference in the antagonist's affinity (K d) to BAR. Both R x (NC: 29.8:1:34.6 vs. PD: 54.9 :k 28.3 fmol/mg protein, t-3.05,df-59, p<0.003) and Rt. (NC: I ! .3:1:9.11 vs. 30. 1-436. I fmol/mg protein, t-2.93, df-59, p<0.005) were higher in PD without differences in %R s. There was a trend for higher K n, Kt. and a significantly higher Kt/ K s ratio in PD patients (NC: 187.2 + 256.1 vs. PD 688.5 + 838.6, t-3.30, dr-59, ig0.001). These results provide evidence for higher BAR density and supereoupling to G s protein, lmipramine significantly decreased R s (Pre: 55.0:1:28.3 vs. Post: 29.0 + 13, t-2.78, df-35, p<0.008) but had no effect on Rt., K H or K L. lmipramine decreased the KL/K s ratio by 50% though it did not reach statistical significance (Pre: 688.5 + 838.6 vs.'Post: 338.1 + 261.6, t-!.29, df-35, p-NS). These observations are consistent with basic science studies showing that imipramine decreases R s and'induces uncoupling of BAR from G s protein.

Chronic nonocclusive coronary artery constriction in rats. Beta-adrenoceptor signal transduction and ventricular failure.

To determine the effects of chronic coronary artery constriction on the relationship between cardiac function and regulation of beta-adrenoceptor signal transduction, the left main coronary artery was narrowed in rats and the animals were killed 5 mo later. An average reduction in coronary luminal diameter of 44% was obtained and this change resulted in an increase in left ventricular end-diastolic pressure and a decrease in positive and negative dP/dt. Significant increases in left and right ventricular weights indicative of global cardiac hypertrophy were observed. Radioligand binding studies of beta-adrenoreceptors, agonist-stimulated adenylate cyclase activity, and ADP ribosylation of 45-kD substrate by cholera toxin were all depressed in the failing left ventricle. In contrast, in the hypertrophic non-failing right ventricle, beta-adrenoreceptor density was preserved and receptor antagonist affinity was increased. In spite of these findings at the receptor level, agonist stimulated cyclic AMP generation was reduced in the right ventricular myocardium. The quantity of the 45-kD substrate was also decreased. In conclusion, longterm nonocclusive coronary artery stenosis of moderate degree has profound detrimental effects on the contractile performance of the heart in association with marked attenuation of adrenergic support mechanisms.

Dietary (n-6) Polyunsaturated Fatty Acids Affect β-Adrenergic Receptor Binding and Adenylate Cyclase Activity in Pig Adipocyte Plasma Membrane

The effect of dietary (n-6) polyunsaturated fatty acids (sunflower oil) on pig adipocyte beta-adrenoreceptor and adenylate cyclase activity was examined. Two adipose sites (subcutaneous and perirenal) were compared. The existence of two affinity classes for beta-adrenoreceptors was evidenced. Adenylate cyclase stimulation by isoproterenol was higher in the perirenal fat than in the subcutaneous fat, in parallel to a higher beta-adrenoreceptor density. When sunflower oil was included in the diet, the adenylate cyclase response to beta-agonists was greater, particularly in perirenal fat, as was the affinity of the adrenoreceptors in their high affinity state. However, the number of beta-adrenoreceptors was lower, suggesting that these are spare receptors. Adenylate cyclase stimulation by 5'-guanylylimidophosphate also revealed site- and diet-specific variations indicating alterations at the Gs-protein level. The adenylate cyclase catalytic activity (reflected by the forskolin-stimulated response) in the control group was higher in the subcutaneous fat than in the perirenal fat. In the sunflower oil-fed pigs, the catalytic activity was greater in the perirenal fat relative to controls, leading to similar values in both adipose tissues of sunflower oil-fed pigs. This indicates that the cyclase catalytic subunit activity also depends on the anatomical site of the fat deposit and is influenced by the diet as well. Correlation between these changes in the adenylate cyclase system are discussed in relationship with alterations in the plasma membrane structure.

Adrenergic receptors in human fetal liver membranes

The adrenergic receptor binding capacities in human fetal and adult livers were measured to investigate the mechanism of the reduced alpha-1 adrenoreceptor response of the liver associated with a reciprocal increase in beta-adrenoreceptor activity in a number of conditions. Alpha- 1 3 and beta-adrenoreceptor density were determined using H-prazosin and 3H-dihydroalprenolol, respectively, as radioligand. Heterogenous populations of beta-adrenoreceptors were found in fetal liver contrast to adult. Decreased alpha-1 and increased beta-receptor density were found which may relate to a decreased level in cellular differentiation. These findings may be important for the investigation of perinatal hypoglycaemia of newborns after treatment of premature labour with beta-mimetics. This is the first demonstration of differences in the ratio of alpha-1 and beta-adrenoreceptors in human fetal liver.

One hour of myocardial ischemia decreases the activity of the stimulatory guanine-nucleotide regulatory protein Gs.

The effect of 1 hour of myocardial ischemia on the function of the stimulatory guanine-nucleotide-binding protein Gs was examined. This study follows our recent finding that myocardial ischemia increases the density of beta-adrenoreceptors in a conscious canine model while having the opposite effect on the activity of adenylate cyclase. Coronary artery occlusion was induced in five conscious dogs and verified by measurement of blood flow using the Doppler and microsphere techniques. Alterations in the level and function of Gs were examined in sarcolemmal membranes prepared from ischemic and nonischemic regions of the left ventricle. After 1 hour of coronary artery occlusion, the functional activity of sarcolemmal Gs, as determined by reconstitution with cyc- membranes, decreased by 27 +/- 7% in the ischemic zone. Cholera toxin labeling performed in parallel with the reconstitution studies demonstrated a similar decrease of 28 +/- 7%. This was associated with decreases in basal activity and decreases in adenylate cyclase activity stimulated by GTP, GTP plus isoproterenol, sodium fluoride, and forskolin. Thus, a defect distal to the beta-adrenoreceptor occurs in the transduction of adrenergic signals to the heart as a consequence of 1 hour of ischemia.

Lymphocyte beta-adrenoreceptor density in patients with unipolar depression and normal controls

Values of binding maximum (B max ) and dissociation constant (K d) of (−)3-[ 125I]iodocyanopindolol (ICYP) were determined in β-adrenergic receptors of membranes of peripheral lymphocytes in 32 patients with unipolar depression (DSM-III-R) and 31 normal controls. Results were analyzed by a two-way Analysis of Covariance method. A significant difference was noted for group assignment (patient versus control , p < 0.05). Mean B max (fmol ICYP bound/mg lymphocyte membrane fraction total protein) of patients was 31.9 ± 3.84 ( se) and controls 46.3 ± 3.92 ( se). A significant interaction was found between group membership and gender (p < 0.05). In the female patient group ( n = 14), mean B max was 30.5 ± 5.79 ( se); in female controls, mean B max was 56.0 ± 5.15 (SE). Differences between male patients and male controls were not significant. Mean values of K d (pmol/liter) showed a trend for patient values to be lower than control values [69.0 ± 73.66 ( se) versus 108.5 ± 14.42 ( se), respectively]. A significant inverse relationship was noted between lymphocyte β-receptor B max and frequency of panic attacks during the depressive episode in 18 patients ( p = 0.05). No relationship was found between values of K d and frequency of panic attacks in these patients. Thus, preliminary evidence is provided for relationships among altered β-adrenergic receptor binding, gender, and indices of panic-anxiety in unipolar depressed patients.

Up-regulation of guinea pig myometrial beta-adrenoreceptors by systemic estradiol and progesterone.

The effects of systemic administration of 17 beta-estradiol (E2) and progesterone (P) on the concentration and affinity of myometrial beta-adrenoreceptors were studied in non-pregnant, previously oophorectomized guinea pigs receiving a continuous infusion of E2, P, a combination of the two hormones, or placebo for 7 days. Myometrial beta-adrenoreceptors were characterized by using (-)-[125I-cyanopindolol as the specific beta-adrenoreceptor ligand. Compared to that in the control group, E2 administration resulted in a 7-fold increase in the density of myometrial beta-adrenoreceptors. Administration of P alone resulted in a significant increase in both beta-adrenergic receptor concentration and the receptor dissociation constant (Kd). Finally, a combination of E2 and P treatment did not result in any synergistic or additive effect for the beta-adrenergic receptors, while the Kd was twice that of the control or E2-treated animals. We conclude that systemic administration of these sex steroid hormones, directly or indirectly, modulates myometrial beta-adrenergic receptor concentrations and their ligand affinity.

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.

Modulating influence of D,L-propranolol on triiodothyronine-induced skeletal muscle protein degradation.

There is evidence suggesting that thyrotoxicosis increases beta-adrenoreceptor density on some target tissues. We have studied the in vivo effect of D,L-propranolol (a nonselective beta-adrenoreceptor blocking agent) on T3-induced enhancement of in situ proteolysis in fast twitch muscle fibers of the rat. Chronic treatment with T3 as opposed to saline resulted in a 76% enhancement of the rate of in situ muscle proteolysis [0.79 +/- 0.04 (n = 8) compared with 0.45 +/- 0.01 (n = 8) nmol tyrosine/mg muscle . 2 h]. Treatment of rats with both T3 and 2 mg propranolol resulted in a 62% reduction in the T3-induced increment in situ muscle proteolysis [0.58 +/- 0.02 (n = 8) vs. 0.79 +/- 0.04]. This significant inhibition by propranolol of T3-induced enhanced proteolytic rates in vitro suggests that this may comprise one component of the observed beneficial clinical effects of beta-blockade in thyrotoxic myopathy.

Beta-adrenoreceptors in rat brown adipose tissue: proportions of beta 1- and beta 2-subtypes.

Binding of (-)-[3H]dihydroalprenolol [( 3H]DHA) to isolated brown adipose tissue (BAT) microsomal membranes was used to estimate beta-adrenoreceptor density, and this was found to be saturable, reversible, and stereospecific. Scatchard analysis indicated a single class of binding sites of equilibrium dissociation constant 2.2 nM, with a maximum number of binding sites of 160-170 fmol/mg protein. These values were unaffected by the age or sex of the animals, and similar Kd values were obtained for binding to heart and lung membranes. The kinetically derived Kd from forward and reverse reactions was 1.4 nM for BAT. Hofstee analysis of displacement of [3H]DHA produced linear plots for propranolol but curvilinear plots for atenolol and ICI 118,551. Atenolol showed 50-fold selectivity for beta 1-receptors and ICI 118,551 50-fold selectivity for beta 2-receptors in heart, lung, and BAT membranes. These plots indicated beta 1:beta 2-receptor ratios of 59:41 for BAT and heart and 25:75 for lung. It is possible that both beta-adrenoreceptor subtypes in BAT may be involved in the activation of thermogenesis in the tissue.

Changes occur in central adrenoreceptor function following long-term morphine treatment and during morphine withdrawal

Radioloigand binding techniques were used in combination with in vivo electrophysiological recording to characterize changes in beta adrenoreceptor activity in various brain areas in rats treated chronically with morphine. Following chronic morphine treatment, the maximum number of specific binding sites for 3H-dihydroalprenolol ( 3H-DHA) in parietal cortex and hippocampus showed a biphasic change, indicating an initial increase and decrease (relative to controls) in beta adrenoreceptors in these regions with time during withdrawal. No appreciable changes were observed in the dissocation constants for 3H-DHA binding. The changes in cortical beta adrenoreceptor density found in early (8 hr) and later phases (32 hr) of withdrawal were paralled by a selective increase and decrease, respectively, in cortical neuron sensitivity to noradrenergic stimulation. These results suggest a possible linkage between changes in central adrenoreceptor function and the formation and/or expression of opiate dependence.

Changes in β-adrenoreceptor density in intact lymphocytes of hypertensive subjects

This paper determines the density of beta-adrenoreceptors of intact lymphocytes from patients with stable essential hypertension and compares it with that of normal subjects. Specific binding of tritium-dihydroalprenolol with intact lymphoctes under certain described conditions was characterized by saturation and high affinity. The results are evidence of a statistically significant increase (by 42%) in beta-adrenoreceptor density of intact lymphocytes in essential hypertension.