Enantioselective resolution of Rac-terbutaline and evaluation of optically pure R-terbutaline hydrochloride as an efficient anti-asthmatic drug.

Terbutaline is a ß2 -adrenoceptor agonist for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Among the two isomers of terbutaline (TBT 2), R-isomer was found to be the potent enantiomer in generating therapeutic effect, while S-isomer has been reported to show side effects. In this study, R-terbutaline hydrochloride (R-TBH 6) was synthesized through chiral resolution from the racemic terbutaline sulfate (rac-TBS 1) with 99.9% enantiomeric excess (ee) in good overall yield (53.6%). Further, R-TBH 6 nebulized solution was prepared in half dosage of Bricanyl®, which is a marketed product of racemic terbutaline and evaluated in vitro aerosol performance and in vivo anti-asthmatic effect on guinea pigs via. pulmonary delivery. From the investigation, it is evident that R-TBH 6 nebulized solution of half dosage performed similar fine aerosol characteristics and anti-asthmatic effect with Bricanyl®.

Impact of systemically active neurohumoral factors on the erectile response of the rat.

INTRODUCTION: Mean arterial pressure (MAP) and specific regulation of penile blood flow are the primary determinants of an erection. While this concept is well recognized, the differential relationship between systemically acting vasoactive factors on arterial pressure and erectile responses is not well described. AIM: The aim of this study was to determine how the modification of systemic levels of neurohumoral factors impacts on the magnitude and efficiency of the erectile response. MAIN OUTCOME MEASURES: The main outcome measures for this study are changes in MAP and intracavernosal pressure (ICP) following electrostimulation of the cavernous nerve. METHODS: Anesthetized adult, male Sprague-Dawley rats were catheterized for measuring MAP (carotid), ICP, and drug administration (vena cava). Erections were induced via cavernous nerve electrostimulation. Vasoactive drug infusions were used to produce changes in MAP levels including: hexamethonium, angiotensin II (ANGII)±hexamethonium, methoxamine±hexamethonium, losartan, MAHMA NONOate, and terbutaline. RESULTS: In general, ICP and MAP were linearly correlated regardless of treatment. Hexamethonium markedly dropped MAP and proportionately decreased the magnitude of the erectile response. ANGII or methoxamine given to hexamethonium-pretreated or untreated rats increased MAP similarly, but produced contrasting effects on erectile responses. ANGII-induced pressor responses were associated with increased erectile responses whereas all methoxamine treatments markedly decreased erectile responses. Depressor changes with losartan or terbutaline, but not MAHMA NONOate, also impacted negatively on the efficiency of the erectile responses at lower arterial pressures. CONCLUSIONS: In general, the magnitude of the erectile responses was found to be dependent upon the level of MAP, although the mechanism by which arterial pressure was changed impacted substantially on the characteristics of the relationship. The major finding was that circulation-wide α-adrenoceptor stimulation was extremely deleterious to erectile responses whereas global stimulation of ANG II receptors was actually proerectile. Overall, the results indicate that neurohumoral specificity in systemic hemodynamic control is also critical in establishing the optimal erectile environment in rats.

Alteration of the circadian rhythm in peak expiratory flow of nocturnal asthma following nighttime transdermal beta2-adrenoceptor agonist tulobuterol chronotherapy.

We investigated the efficacy of nighttime transdermal tulobuterol (beta2-adrenoceptor agonist) chronotherapy for nocturnal asthma by assessing changes both in the frequency of symptoms and features of the circadian rhythm in peak expiratory flow (PEF), a measure of airway caliber. Thirteen patients with nocturnal asthma were evaluated before and during tulobuterol patch chronotherapy, applied once daily in the evening for 6 consecutive days. Patients were asked to record their PEF every 4h between 03:00 and 23:00 h for one day. Circadian rhythms in PEF were examined by group-mean cosinor analysis. The group average PEF at 03:00 h, the time during the 24 h when PEF is generally the poorest, before the application of the chronotherapy, when asthma was unstable and nocturnal symptoms frequent, was 276 +/- 45 L/min. Application of the tulobuterol patch at nighttime significantly increased (p < 0.001) the 03:00 h group average PEF to 363 +/- 67 L/min. Significant circadian rhythms in PEF were observed during the span of study when nocturnal symptoms were frequent as well as with the use of the tulobuterol patch. Before the initiation of tulobuterol chronotherapy, the bathyphase (trough time of the circadian rhythm) in PEF narrowed to around 04:00h, and the group circadian amplitude was 28.8 L/min. In contrast, the group circadian amplitude significantly (p < 0.01) decreased to 10.4 L/min, and the 24 h mean PEF increased significantly with tulobuterol patch chronotherapy. These changes indicate that tulobuterol chronotherapy significantly increased both the level and stability of airway function over the 24 h. The circadian rhythm in PEF varied with the severity and frequency of asthmatic symptoms with and without the nighttime application of the tulobuterol patch medication. We conclude that the parameters of the circadian rhythm of PEF proved useful both in determining the need for and effectiveness of tulobuterol chronotherapy for nocturnal asthma.

Differential bronchodilatory effects of terbutaline, diltiazem, and aminophylline in canine intraparenchymal airways.

OBJECTIVES: Intraparenchymal airways are involved in air flow regulation. Relaxation of intraparenchymal airways to volatile anesthetics varied by topographic location. This study was conducted to determine whether other bronchodilators (terbutaline, diltiazem, and aminophylline) relax bronchiolus to a greater degree than bronchus, as seen with volatile anesthetics. DESIGN: In vitro, controlled, randomized study. SETTING: Animal research laboratory. SUBJECTS: Adult dogs (n = 9). INTERVENTIONS: Proximal (outer diameter, 4-6 mm) and distal (outer diameter, 0.8-1.5 mm) airway rings of dogs were contracted in tissue baths with the effective concentration of acetylcholine that produces half the maximum response. Airway relaxant dose-response curves were constructed to measure isometric tension after administration of terbutaline (concentration range, 10(-8) to 10(-4) M), diltiazem (concentration range, 3 x 10(-7) to 1 x 10(-4) M), and aminophylline (concentration range, 10(-7) to 10(-4) M). MEASUREMENTS AND MAIN RESULTS: All three bronchodilators caused relaxation of the proximal and distal airways. At the maximum dose, diltiazem (maximum relaxation, 95%+/-2% [proximal], 94%+/-6% [distal]; p > .05) was the most efficacious, followed by terbutaline (maximum relaxation, 72%+/-13% [proximal], 55%+/-9% [distal]; p < .05) and aminophylline (maximum relaxation, 32%+/-10% [proximal], 35%+/-18% [distal]; p > .05. At the concentrations tested, they were equally efficacious. No significant differences in relaxation between proximal and distal airways were noted with diltiazem or aminophylline in the entire dose range. However, terbutaline relaxed the distal airway more than the proximal airway in the entire dose range. CONCLUSIONS: The results demonstrate that only terbutaline showed a differential airway relaxant effect between proximal and distal airways, as seen with volatile anesthetics.

Effects of beta 2-agonist- and dexamethasone-treatment on relaxation and regulation of beta-adrenoceptors in human bronchi and lung tissue.

1. Long-term treatment with beta 2-adrenoceptor agonists can lead to a decreased therapeutic efficacy of bronchodilatation in patients with obstructive pulmonary disease. In order to examine whether or not this is due to beta-adrenoceptor desensitization, human bronchial muscle relaxation was studied in isolated bronchial rings after pretreatment with beta 2-adrenoceptor agonists. Additionally, the influence of pretreatment with dexamethasone on desensitization was studied. 2. The effect of beta 2-agonist incubation alone and after coincubation with dexamethasone on density and affinity of beta-adrenoceptors was investigated by radioligand binding experiments. 3. In human isolated bronchi, isoprenaline induces a time- and concentration-dependent beta-adrenoceptor desensitization as judged from maximal reduction in potency by a factor of 7 and reduction of 73 +/- 4% in efficacy of isoprenaline to relax human bronchial smooth muscle. 4. After an incubation period of 60 min with 100 mumol l-1 terbutaline, a significant decline in its relaxing efficacy (81 +/- 8%) and potency (by a factor 5.5) occurred. 5. Incubation with 30 mumol l-1 isoprenaline for 60 min did not impair the maximal effect of a subsequent aminophylline response but led to an increase in potency (factor 4.4). 6. Coincubation of dexamethasone with isoprenaline (120 min; 30 mumol l-1) preserved the effect of isoprenaline on relaxation (129 +/- 15%). 7. In radioligand binding experiments, pretreatment of lung tissue for 60 min with isoprenaline (30 mumol l-1) resulted in a decrease in beta-adrenoceptor binding sites (Bmax) to 64 +/- 1.6% (P < 0.05), while the antagonist affinity (KD) for [3H]-CGP-12177 remained unchanged. 8. In contrast, radioligand binding studies on lung tissue pretreated with either dexamethasone (30 mumol l-1) or isoprenaline (30 mumol l-1) plus dexamethasone (30 mumol l-1) for 120 min did not lead to a significant change of Bmax (160 +/- 22.1% vs 142.3 +/- 28.7%) or KD (5.0 nmol l-1 vs 3.5 nmol l-1) compared to the controls. 9. In conclusion, pretreatment of human bronchi with beta-adrenoceptor agonists leads to functional desensitization and, in lung tissue, to down-regulation of beta-adrenoceptors. This effect can be counteracted by additional administration of dexamethasone. Our model of desensitization has proved useful for the identification of mechanisms of beta-adrenoceptor desensitization and could be relevant for the evaluation of therapeutic strategies to counteract undesirable effects of long-term beta-adrenoceptor stimulation.

Lipolysis in human fat cells obtained under local and general anesthesia.

OBJECTIVES: As adipose tissue is usually obtained during local or general anesthesia in clinical studies, these two forms of anesthesia were presently compared as regards lipolysis induced by catecholamines in isolated human fat cells. DESIGN: Fat samples from the abdominal subcutaneous region were obtained first during local anesthesia (lidocaine) given so that the anesthetic agent did not influence lipolysis and second, during gastric banding under general anesthesia (propofol) immediately after skin incision. SUBJECTS: Eleven obese patients, drug free and otherwise healthy. MEASUREMENTS: Isolated fat cells were incubated in the presence or absence of increasing concentrations of different lipolysis agents, acting at adrenoceptor or various post-receptor levels in the lipolytic cascade. Glycerol release to the incubation medium was measured as an index of lipolysis. RESULTS: All agonists caused a concentration dependent increase (terbutaline, dobutamine, CGP 12177, forskolin, dibutyryl cyclic AMP, isoprenaline and noradrenaline) or inhibition (clonidine) of glycerol release. The comparison of data from local and general anesthesia procedures showed no statistical difference in glycerol response for any of the drugs used. CONCLUSIONS: Adrenergic regulation of lipolysis is not influenced by the mode of sampling, at least not in subcutaneous fat cells of obese subjects obtained during local anesthesia with lidocaine as compared to general anesthesia with propofol.

X-ray microanalysis of myometrium in parturient women at term.

The purpose of this study was to investigate the elemental composition of myometrial cells from term parturient women with normal and dysfunctional labour. Myometrial biopsies were obtained from forty-four term pregnant women undergoing Cesarean section. The patients were categorized according to uterine activity as follows: before labour, normal labour, labour successfully augmented by oxytocin, oxytocin-resistant labour, and labour arrested by terbutaline. X-ray microanalysis of freeze-dried sections (16 mu m thick) of the myometrium was carried out. An increase in intracellular phosphorus level (p < .01) was noted in the normal labour group compared to before labour. In patients with normal labour, higher phosphorus (p < .009) and potassium (p < .005) were found compared to oxytocin resistant labour. Patients with oxytocin resistant labour had lower intracellular potassium (p < .0006) and phosphorus (p < .02), and higher chloride (p < .05) and sodium (p < .03) compared to levels found in patients who responded to oxytocin treatment. In dysfunctional (oxytocin-resistant) labour the ion distribution in the myometrial cells might be disturbed. The reduced level of potassium and phosphorus together with the high sodium and chloride levels found in patients with oxytocin resistant labour may be connected to an impairment in sodium-potassium pump and muscle dysfunction, clinically diagnosed as dystocia.

Pharmacodynamic modelling of the drug-induced downregulation of a beta 2-adrenoceptor mediated response and lack of restoration of receptor function after a single high dose of prednisone.

Changes in beta 2-adrenoceptor function by chronic dosing of beta 2-mimetics and the possible influence of a single dose of prednisone have been studied as changes over time in the concentration-effect relationship of the beta 2-adrenoceptor agonist terbutaline. Hypokalaemia was used as the specific beta 2-adrenoceptor mediated effect. 8 healthy volunteers were given subcutaneous terbutaline 0.01 mg.kg-1 BW on 3 occasions over a 10-day experimental protocol: 1 Control experiment on Day 1; 2 After 7 days of oral terbutaline 5 mg t.i.d. (Day 8); and 3 After 8 days on oral terbutaline and 12 h after prednisone 100 mg orally (Day 10). The time course of the terbutaline concentrations and hypokalaemia was related using a pharmacokinetic-pharmacodynamic model. A sigmoid and a threshold Emax model were used to relate drug concentrations to effects. The oral terbutaline treatment caused a 35% increase in the distribution volume of SC terbutaline. After one week on oral terbutaline the concentration-effect relationship was shifted to the right and was steeper, with a higher EC50 of terbutaline and higher values for the apparent threshold concentration. These observations are compatible with a decrease in receptor numbers after 7 days of terbutaline in a system characterised by the presence of spare receptors. The data after prednisone pretreatment showed an apparent decline in the baseline plasma potassium concentrations that could be included in the Emax model. There was no change in the concentration-effect relationship 12 hours after prednisone.

Rat model for the study of penile erection: pharmacologic and electrical-stimulation parameters.

We report the use of a modified rat model for the study of the mechanisms of penile erection. In 92 Sprague-Dawley rats, the cavernous nerve was stimulated with different pulse intensities and frequencies, and the intracavernous pressure, time to maximal pressure and total duration of tumescence were measured. A maximal response was elicited at 20 pulses per second (pps) and 1.5 mA. Using this as 100%, we determined the relative pressure responses obtained with other frequencies: 5 pps, 57.3% (p = 0.007), 10 pps, 84.9% (p = 0.043); 30 pps, 99.5% (p = 0.832); 40 pps, 97.8% (p = 0.168); 50 pps, 90.9% (p = 0.021); 100 pps, 76.1% (p < 0.001). The time to maximal pressure varied with different frequencies, but was in all cases significantly different from the 20-pps response. Erection time during continuous cavernous nerve stimulation was significantly longer with frequencies below 20 pps (10 and 5 pps). In 30 rats, the physiologic response to intracavernous injection (0.03 ml) of acetylcholine, atropine, guanethidine, norepinephrine, phenylephrine, papaverine, terbutaline (intravenous also) and phentolamine was measured. Papaverine caused a dose-dependent rise in pressure; acetylcholine, atropine (a parasympathetic blocking agent) and guanethidine all had minimal effects. Phentolamine and norepinephrine increased systemic blood pressure, whereas phenylephrine decreased the intracavernous pressure in response to electrostimulation significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Amine oxidase-mediated cytotoxicity of spermine and epinephrine to human myelogenous leukemia K562 cells.

The effects of spermine and beta-adrenoceptor agonists (epinephrine, terbutaline and orciprenaline) in the presence and in the absence of fetal bovine serum (FBS) on human myelogenous leukemia K562 cells viability (V) and survival (N/Nc) were examined. Spermine-FBS significantly decreased both V and N/Nc of K562 cells. Aminoguanidine (AG), an amine oxidase inhibitor, and reduced form of glutathione abolished this effect demonstrating that the spermine-FBS action was amine oxidase-mediated. Epinephrine expressed a strong cytotoxicity to K562 cells which was abolished by pargyline, a specific monoamine oxidase (MAO) inhibitor, as well as by reduced form of glutathione. Terbutaline and orciprenaline exerted no cytotoxic activity to K562 cells cultured in FBS-supplemented medium, independently on the presence of spermine. However, terbutaline at concentrations of over 1 mmol strongly inhibited the cytotoxic effect on spermine-FBS. The relationship between cytotoxicity and chemical structure of beta-adrenoceptor agonists was discussed especially with respect to their stability toward oxidation.

Calcium channel blockers and terbutaline--a positive interaction.

The role of two calcium channel blockers, nifedipine and verapamil was investigated in patients of bronchial asthma. Both the drugs given orally produced an insignificant rise in PEFR, FEF25-75% and FEV1. Given along with terbutaline, however, these drugs produced significantly greater increase in PEFR, FEF25-75% and FEV1 as compared to patients receiving terbutaline alone. The two calcium channel blockers also inhibited the terbutaline induced tremors and palpitation.

Intrahypothalamic injections of norepinephrine facilitate feline affective aggression via alpha 2-adrenoceptors.

The purpose of this study was to investigate the effects of noradrenergic agents infused into the anterior hypothalamus on feline affective defense responses elicited by electrical stimulation of the ventromedial hypothalamus. Anterior hypothalamic sites which are known to receive inputs from both the ventromedial hypothalamus and ascending noradrenergic pathways were selected for pharmacological analysis. Intracerebral infusions of NE (1.2-2.4 nmol) into the anterior hypothalamus significantly reduced the threshold current required to elicit the hissing component of affective defense via electrical stimulation of the ventromedial hypothalamus. Maximal threshold reductions (17 +/- 3% to 20 +/- 3%) were observed 30 min following infusion. Anterior hypothalamic infusions of clonidine facilitated feline affective defense by reducing hissing current thresholds by 18 +/- 4%. Clonidine-induced changes in response thresholds parallel those obtained with NE. Both NE-induced and clonidine-induced reductions in current thresholds were reversible by pre- and post-treatment of the anterior hypothalamic sites with yohimbine. These results demonstrate that the reductions in response thresholds are mediated by post-synaptic alpha 2-adrenoceptors located within the anterior hypothalamus. Thus the noradrenergic system may play an important role in the regulation of affective aggressive behavior.

Effects of beta-endorphin, met-enkephalin, and dynorphin A on basal and stimulated insulin secretion in the mouse.

Since opioid peptides and opiate receptors have been demonstrated in the pancreatic islets, we investigated the effects of beta-endorphin, met-enkephalin, and dynorphin A, on basal and stimulated insulin secretion in the mouse. Each of the three opioid peptides was injected intravenously (0.06-64 nmol/kg) alone or together with each of the three insulin releasing agents glucose (2.8 mmol/kg), carbachol (cholinergic agonist, 0.16 mumol/kg), or terbutaline (beta 2-adrenoceptor agonist, 3.6 mumol/kg). It was found that beta-endorphin, met-enkephalin, and dynorphin A were all without effect on basal plasma insulin levels, except a slight elevation by beta-endorphin induced at 2 min after its injection at 64 nmol/kg (to 41 +/- 2 microU/mL vs 28 +/- 4 microU/mL in controls; p less than 0.05). Glucose- and terbutaline-induced insulin secretion were inhibited by beta-endorphin at the lower dose levels of 0.25 (p less than 0.01) and 1 nmol/kg (p less than 0.05). This effect was counteracted by the opiate receptor antagonist naloxone (500 micrograms/kg). In contrast, beta-endorphin at the high dose levels of 16 and 64 nmol/kg augmented the glucose- and terbutaline-induced insulin secretion (p less than 0.05). Carbachol-induced insulin secretion was not affected by beta-endorphin at the lower dose levels but augmented by the peptide at 64 nmol/kg (p less than 0.01). Met-enkephalin inhibited glucose- (p less than 0.01) and terbutaline- (p less than 0.05) induced insulin secretion at the high dose rates of 16 and 64 nmol/kg, but the peptide was without effect on carbachol-induced insulin secretion. The inhibitory effects were counteracted by naloxone. Dynorphin A did not affect stimulated insulin secretion at any of the dose levels tested. In summary, in the mouse 1. beta-Endorphin at low dose levels inhibits and at high dose levels augments stimulated insulin secretion; 2. Met-enkephalin inhibits stimulated insulin secretion; and 3. Dynorphin A does not affect insulin secretion. It is suggested that the main influence of beta-endorphin and met-enkephalin under in vivo conditions in the mouse is to inhibit stimulated insulin secretion.

The effect of various drugs on canine ureteric peristalsis.

Using an intact concious animal model the effect of various drugs on the rate of canine ureteric peristalsis was studied. The drugs found to reduce consistently the rate of ureteric peristalsis were diazoxide, terbutaline, and ritodrine. Ritodrine was the most consistent, having a prolonged effect and reducing the rate of ureteric peristalsis to 50% of the rates observed in control experiments.

Glucocorticoids and beta-adrenergic-receptor agonists: their combined effect on fetal rabbit lung surfactant.

In a previous study on pregnant rabbits (Am J Obstet Gynecol 1983; 147:437) we found that a prolonged infusion of the beta 2-adrenergic-receptor agonist terbutaline would first cause a release of fetal pulmonary surfactant, so that more was available in the airways. However, the airway fluid then contained less surfactant, indicating a depletion of stores. Since terbutaline is often used in high doses as a tocolytic agent, surfactant depletion could be a serious side effect. With further studies on rabbits, we wanted to test the hypothesis that with an accelerated surfactant synthesis, achieved with glucocorticoids, the increased release, evoked with the terbutaline, would never cause a depletion of the surfactant stores. Our results supported this hypothesis. Betamethasone, administered to the pregnant doe on the twenty-sixth and twenty-seventh days of gestation, 0.1 mg/kg, increased compliance of the fetal lungs, and more phospholipid phosphorus could be lavaged from the airways. These effects were further increased when, following steroid administration, the doe was infused with terbutaline. Depletion of the surfactant stores was never seen when betamethasone was given prior to the beta-adrenergic-receptor agonist.

Terbutaline modulation of human allergic skin reactions.

Terbutaline, a preferential beta 2-adrenergic agonist, has been shown to inhibit allergen-induced histamine release in vitro. In contrast, orally administered therapeutic doses of terbutaline do not inhibit antigen-induced wheal and flare reactions. We studied the effects of local terbutaline on antigen-induced whealing response, histamine release, cellular inflammatory response, and ultramicroscopic mast cell changes in antigen-challenged skin sites in ragweed-sensitive subjects. Results showed that ragweed challenge significantly induced increased histamine release in all subjects. In contrast, no such histamine release was observed at sites challenged with antigen in the presence of terbutaline. Thus locally applied terbutaline in nontoxic doses modulates mediator release in certain allergic reactions.

Short-term regulation of fatty acid synthesis in isolated alveolar type II cells from adult rat lung. Effects of free fatty acids and hormones.

We measured the total rate of fatty acid synthesis in alveolar type II cells freshly isolated from the lungs of adult rats. The rate of incorporation of 3H from 3H2O into cellular fatty acids was linear during 3-hr incubations and was very brisk [18 ng-atoms 3H/10(6) cells/hr +/- 2 (mean +/- SD, n = 23)]. When the nutrient medium (Minimum Essential Medium) was supplemented with various hormones or free fatty acids, the long-chain fatty acids (C14-C20) caused a decrease in the rate of 3H incorporation to a variable degree depending on the species of fatty acid. Stearate (10(-4) M) and palmitate (10(-4) M) caused the greatest inhibition of de novo cellular fatty acid synthesis, followed by myristate, arachidonate, and oleate. Insulin (10(-7) M), glucagon (10(-8) M), terbutaline (10(-5) M), 8-bromo-cyclic AMP (10(-3) M), the essential fatty acid linoleate (10(-4) M), and the medium-chain-free fatty acids laurate and octanoate (10(-4) M) did not alter the rate of fatty acid synthesis in type II cells. We demonstrated that the alveolar type II cell is a major lipogenic cell type in the rat. We also demonstrated that the availability of preformed fatty acids in the extracellular milieu is one factor regulating the rate of fatty acid synthesis in these cells.