In vitro assessment of triterpenoids NVX-207 and betulinyl-bis-sulfamate as a topical treatment for equine skin cancer.

Equine sarcoid (ES) is the most prevalent skin tumor in equids worldwide. Additionally, aging grey horses frequently suffer from equine malignant melanoma (EMM). Current local therapies targeting these skin tumors remain challenging. Therefore, more feasible topical treatment options should be considered. In order to develop a topical therapy against ES and EMM, betulinyl-bis-sulfamate and NVX-207, derivatives of the naturally occurring betulin and betulinic acid, respectively, were evaluated for their antiproliferative (crystal violet staining assay), cytotoxic (MTS assay) and apoptotic (AnnexinV staining, cell cycle investigations) effects on primary ES cells, EMM cells and equine dermal fibroblasts in vitro. The more potent derivative was assessed for its in vitro penetration and permeation on isolated equine skin within 30 min and 24 h using Franz-type diffusion cells and HPLC analysis. Betulinyl-bis-sulfamate and NVX-207 inhibited the proliferation and metabolism in ES cells, EMM cells and fibroblasts significantly (p < 0.001) in a time- and dose-dependent manner. NVX-207 had superior anticancer effects compared to betulinyl-bis-sulfamate. Both compounds led to the externalization of phosphatidylserines on the cell membrane and DNA fragmentation, demonstrating that the effective mode of action was apoptosis. After 48 h of treatment with NVX-207, the number of necrotic cells was less than 2% in all cell types. Detected amounts of NVX-207 in the different skin layers exceeded the half-maximal inhibitory concentrations calculated by far. Even though data obtained in vitro are auspicious, the results are not unconditionally applicable to the clinical situation. Consequently, in vivo studies are required to address the antitumoral effects of topically applied NVX-207 in ES and EMM patients.

[The benefits of carvedilol therapy in the treatment of patients with high cardiovascular risk]. / A carvedilolterápia elonyei magas cardiovascularis kockázatú betegek kezelése során.

Among the variety of cardiologic pharmacological therapy options, beta-blockers stand on a prominent position. There are several reasons for this. On one hand they have numerous indication rounds, even though professional guidelines have recently tended to de-emphasize them for treatments of hypertension without complication or comorbidity. However, in addition to hypertonic cases associated with cardiac complication, they play a fundamental role in treating heart failure and arrhythmia and the different clinical manifestations (stable angina pectoris, myocardial state) of ischemic heart disease. The decade long development of the pharmacological group made its hemodynamic effects ever more refined. On the other hand we must not neglect the fact that more and more features came to light that positively influence the outcome of cardiovascular diseases. Verification of these latter features in numerous multicentric studies showed how to achieve a beneficial effect on survivability, independent on even hemodynamic effects during beta-blocker therapy.

A single oral dose of flavan-3-ols enhances energy expenditure by sympathetic nerve stimulation in mice.

Numerous clinical studies have found that ingestion of chocolate reduces the risk of metabolic syndrome, however, the mechanisms were remain unclear. We have reported that a single dose of a flavan-3-ol fraction derived from cocoa (FL) enhanced energy expenditure (EE) and increased the mRNA expression levels of uncoupling proteins (UCPs) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), and the protein level of phosphorylated AMP-activated protein kinase (AMPK)α in tissues, along with plasma adrenaline level. In the present study, we examined whether the EE enhancing activity of FL is mediated by adrenergic effect using several adrenalin receptor (AR) blockers. In the first study, mice were butoxamine, as ß2AR blocker, with vehicle or 10mg/kg FL orally. We found that pretreatment with butoxamine prevented the increases of EE, the mRNA expression of UCP-3, and phosphorylated AMPKα that were induced in the gastrocnemius muscle of mice by 10mg/kg FL. Secondly, mice were given SR52930, as ß3AR blocker. Pretreatment with SR52930 prevented the increases of EE, the mRNA expression of UCP-3, and phosphorylated AMPKα that were induced in the gastrocnemius muscle of mice by 10mg/kg FL. Pretreatment with a combination of both blockers also reduced the increments in mRNA expression levels of UCPs and PGC-1α, however, phosphorylated AMPKα in skeletal muscle was rather increased. These results suggest that the ability of a single oral dose of FL to enhance metabolic activity is mediated by sympathetic nerve system (SNS).

In vitro anticancer activity of Betulinic acid and derivatives thereof on equine melanoma cell lines from grey horses and in vivo safety assessment of the compound NVX-207 in two horses.

Betulinic acid, a pentacyclic triterpene, and its derivatives are promising compounds for cancer treatment in humans. Melanoma is not only a problem for humans but also for grey horses as they have a high potential of developing melanoma lesions coupled to the mutation causing their phenotype. Current chemotherapeutic treatment carries the risk of adverse health effects for the horse owner or the treating veterinarian by exposure to antineoplastic compounds. Most treatments have low prospects for systemic tumor regression. Thus, a new therapy is needed. In this in vitro study, Betulinic acid and its two derivatives B10 and NVX-207, both with an improved water solubility compared to Betulinic acid, were tested on two equine melanoma cell lines (MelDuWi and MellJess/HoMelZh) and human melanoma (A375) cell line. We could demonstrate that all three compounds especially NVX-207 show high cytotoxicity on both equine melanoma cell lines. The treatment with these compounds lead to externalization of phosphatidylserines on the cell membrane (AnnexinV-staining), DNA-fragmentation (cell cycle analysis) and activation of initiator and effector caspases (Caspase assays). Our results indicate that the apoptosis is induced in the equine melanoma cells by all three compounds. Furthermore, we succeed in encapsulating the most active compound NVX-207 in 2-Hydroxyprolyl-ß-cyclodextrine without a loss of its activity. This formulation can be used as a promising antitumor agent for treating grey horse melanoma. In a first tolerability evaluation in vivo the formulation was administered every one week for 19 consecutive weeks and well tolerated in two adult melanoma affected horses.

Assessment of the potential drug-drug interaction between carvedilol and clopidogrel mediated through intestinal P-glycoprotein.

The most widely prescribed oral antiplatelet agent, clopidogrel, shows high interindividual variability resulting in an increased risk of cardiovascular events in the patients with reduced platelet inhibition. The purpose of this study was to investigate the role of the P-glycoprotein (P-gp) efflux pump in limiting the intestinal permeability of clopidogrel and the effect of a ß-blocker, namely, carvedilol, on its intestinal transport. Effective permeabilities (Peff) of clopidogrel and carvedilol were investigated in the proximal jejunum and distal ileum of rats using an in situ intestinal perfusion model. Peff values of clopidogrel and carvedilol were found to be concentration dependent with decreased Peff values at the low perfusate concentrations. Coperfusion with the P-gp inhibitors verapamil (100 µM) and carvedilol (10 µM) significantly increased the Peff of clopidogrel in the jejunum (8.31±0.20 x 10-5 and 6.98±0.75 x 10-5 vs. 3.60±0.51 x 10-5, respectively) and ileum (9.08±2.19 x 10-5 and 8.35±1.58 x 10-5 vs. 3.85±0.15 x 10-5, respectively). However, at the highest concentration tested (30 µM), clopidogrel exhibited 3 and 1.4 times higher Peff than those of metoprolol, an FDA high permeability reference standard, in the jejunum and ileum, respectively. Overall, this study indicates that the efflux function appears not to have a significant impact on the in vivo intestinal absorption of clopidogrel due to the saturation of P-gp, suggesting no clinically relevant interaction between carvedilol and clopidogrel mediated through P-gp at intestinal level.

Noninvasive Assessment of Atrioventricular Nodal Function: Effect of Rate-Control Drugs during Atrial Fibrillation.

BACKGROUND: During atrial fibrillation (AF), conventional electrophysiological techniques for assessment of refractory period or conduction velocity of the atrioventricular (AV) node cannot be used. We aimed at evaluating changes in AV nodal properties during administration of tecadenoson and esmolol using a novel ECG-based method. METHODS: Fourteen patients (age 58 ± 8 years, 10 men) with AF were randomly assigned to either 75 or 300 µg intravenous tecadenoson. After tecadenoson wash-out, patients received esmolol continuously (100 µg/kg per min for 10 mins, then 50 µg/kg per min for 50 mins). Atrial fibrillatory rate (AFR) and heart rate (HR) were assessed in 15-min segments. Using the novel method, we assessed the absolute refractory periods of the slow and fast pathways (aRPs and aRPf) of the AV node to produce an estimate of the functional refractory period. RESULTS: During esmolol infusion, AFR and HR were significantly decreased and the absolute refractory period was significantly prolonged in both pathways (aRPs: 387 ± 73 vs 409 ± 62 ms, P < 0.05; aRPf: 490 ± 80 vs 529 ± 58 ms, P < 0.05). During both tecadenoson doses, HR decreased significantly and AFR was unchanged. Both aRPs and aRPf were prolonged for a 75 µg dose (aRPs: 322 ± 97 vs 476 ± 75 ms, P < 0.05; aRPf: 456 ± 102 vs 512 ± 55 ms, P < 0.05) whereas a trend toward prolongation was observed for a 300 µg dose. CONCLUSIONS: The estimated parameters reflect expected changes in AV nodal properties, i.e., slower conduction through the AV node for tecadenoson and prolongation of the AV node refractory period for esmolol. Thus, the proposed approach may be used to assess drug effects on the AV node in AF patients.

Hypotensive anesthesia with esmolol. Assessment of hemodynamics, consumption of anesthetic drugs, and recovery.

OBJECTIVE: To assess the effect of esmolol added to propofol-remifentanil combination for hypotensive anesthesia on hemodynamic conditions, consumption of anesthetic drugs, and recovery, during elective septorhinoplasty. METHODS: This prospective, randomized study was carried out at Gazi University, Faculty of Medicine, Ankara, Turkey in 2005. Following Institutional Ethical Committee approval, 40 American Society of Anesthesiologists (ASA) I patients were divided into 2 equal groups group remifentanil infusion RP and group esmolol infusion (RP-E). After anesthesia induction with propofol (2-2.5 mg/kg), the mean arterial pressure was aimed to be between 50 mm Hg and 65 mm Hg for controlled hypotensive anesthesia in both groups. In group RP, a remifentanil infusion of 0.1-0.5 microg/kg/min was titrated, following a bolus of 1 microg/kg; for group RP-E, an esmolol infusion of 100-300 mg/kg/min was titrated, following a bolus of 500 microg/kg; to achieve a target blood pressure. In addition, propofol was infused according to depth of anesthesia to maintain anesthesia in both groups. Electrocardiography, heart rate, blood pressure, cardiac output, and consumption of anesthetic drugs were recorded. Postoperatively, recovery times, visual analog pain scores, and side effects were observed. RESULTS: The decrease in the intraoperative heart rate was more significant in group RP-E than in group RP. The remifentanil consumption was much lower in group RP-E. The recovery times were similar in both groups. CONCLUSION: Addition of esmolol to propofol-remifentanil combination leads to a decrease in remifentanil consumption, without a decrease in cardiac output during hypotensive anesthesia.

Global diastolic strain rate for the assessment of left ventricular relaxation and filling pressures.

BACKGROUND: Diastolic strain rate (SR) measurements that comprise all left ventricular (LV) segments are advantageous over myocardial velocity for assessment of diastolic function. Mitral early diastolic velocity (E)/SR ratio during the isovolumetric relaxation (IVR) period can be used to estimate LV filling pressures. METHODS AND RESULTS: Simultaneous echocardiographic imaging and LV pressure measurements (7F catheters) were performed in 7 adult dogs. Loading conditions were altered by saline infusion and caval occlusion, and lusitropic state was changed by dobutamine and esmolol infusion. A curve depicting global SR was derived from each of the 3 apical views, and SR was measured during IVR (SR(IVR)) and early LV filling (SR(E)). SR(IVR) had a strong correlation with time constant of LV pressure decay during the IVR period (tau) (r=-0.83, P<0.001), whereas SR(E) was significantly related to LV end-diastolic pressure (r=0.52, P=0.005) in the experimental stages where tau was <40 ms. In 50 patients with simultaneous right heart catheterization and echocardiographic imaging, mitral E/SR(IVR) ratio had the best correlation with mean wedge pressure (r=0.79, P<0.001), as well as in 24 prospective patients (r=0.84, P=0.001). E/SR(IVR) was most useful in patients with ratio of E to mitral annulus early diastolic velocity (E/Ea ratio) 8 to 15 and was more accurate than E/Ea in patients with normal ejection fraction and regional dysfunction (both P<0.01). CONCLUSIONS: Global SR(IVR) by 2-dimensional speckle tracking is strongly dependent on LV relaxation. E/SR(IVR) can predict LV filling pressures with reasonable accuracy, particularly in patients with normal ejection fraction and in those with regional dysfunction.

Chronic effects of AJ-9677 on energy expenditure and energy source utilization in rats.

The effects of AJ-9677 on metabolic parameters were examined in rats that had or had not been chronically treated with this beta3-adrenoceptor agonist. A challenge administration of AJ-9677 increased both the temperature of brown adipose tissue and energy expenditure in both groups of rats. However, whereas the former effect was subject to desensitization, the latter effect was augmented by prior chronic administration of AJ-9677. Whereas a challenge administration of AJ-9677 induced a decrease in the respiratory quotient that persisted for at least 15 h in rats pretreated with vehicle, the initial decrease in this parameter lasted for only 4 h in rats pretreated with AJ-9677. These results suggest that, in rats subjected to chronic treatment with AJ-9677, a challenge administration of this drug increased energy expenditure by stimulation not only of fat oxidation but also of glucose oxidation.

A parametric assessment of GABA antagonist effects on paired-pulse facilitation in the rat anterior cingulate cortex.

Paired-pulse facilitation (PPF) is a form of short-term plasticity that can be used qualitatively to characterize the synaptic effects of neuroactive compounds. As we have shown previously, CNQX has a marked effect on PPF which can be measured quantitatively. The aim of the present study was to examine quantitatively possible differences in the effects of the post- and pre-synaptic GABA antagonists on PPF in vitro. Experiments were performed on slices taken from the coronal anterior cingulate cortex (ACC) of Sprague-Dawley rats. The stimuli consisted of a pair of biphasic pulses with an inter-pulse interval of 40ms. Evoked extracellular field potentials in layers 2/3 of the ACC were recorded. Quantitative assessment of PPF was achieved by calculating two parameters, the PPFmax (theoretical maximal PPF) and the Stmax (stimulus intensity that produces the PPFmax). Picrotoxin treatment produced increases in both the PPFmax and Stmax, by increasing the stimulus producing the half-maximal effect. In contrast, CGP-55845 treatment produced an increase in only the PPFmax, which was due to an alteration in the asymptotic values of the response amplitudes. Our findings show that the effect of different GABA receptor antagonists on short-term synaptic facilitation in the ACC may be assessed and specified quantitatively.

Quantitative assessment of regional myocardial function in mice by tissue Doppler imaging: comparison with hemodynamics and sonomicrometry.

BACKGROUND: Tissue Doppler imaging (TDI) is a novel echocardiographic method to quantify regional myocardial function. The objective of this study was to assess whether myocardial velocities and strain rate (SR) could be obtained by TDI in mice and whether these indices accurately quantified alterations in left ventricular (LV) systolic function. METHODS AND RESULTS: TDI was performed in 10 healthy mice to measure endocardial (v(endo)) and epicardial systolic velocities and SR. In further experiments, TDI indices were compared with dP/dt(max) and with sonomicrometer-derived regional velocities, at rest and after administration of dobutamine or esmolol. TDI indices were also studied serially in 8 mice before and 4 and 7 hours after endotoxin challenge. Myocardial velocities and SR were obtained in all mice with low measurement variability. TDI indices increased with administration of dobutamine (v(endo) from 2.2+/-0.3 to 3.8+/-0.2 cm/s [P<0.01]; SR from 12+/-2 to 20+/-2 s(-1) [P<0.05]) and decreased with administration of esmolol (v(endo) 1.4+/-0.2 cm/s [P<0.05]; SR 6+/-1 s(-1) [P<0.01]). Both indices correlated strongly with dP/dt(max) (r2=0.79 for SR and r2= 0.69 for v(endo); both P<0.0001). SR and shortening fraction were predictors of dP/dt(max) even after adjustment for the confounding effect of the other variables. V(endo) correlated closely with sonomicrometer-measured velocity (r2=0.71, P<0.0005). After endotoxin challenge, decreases in both v(endo) and SR were detected before decreases in shortening fraction became manifest. CONCLUSIONS: Myocardial velocities and SR can be measured noninvasively in mice with the use of TDI. Both indices are sensitive markers for quantifying LV global and regional function in mice.

Betablockers in heart failure: Carvedilol Safety Assessment (CASA 2-trial).

BACKGROUND: Betablockers are a cornerstone in the treatment of patients with chronic heart failure (CHF). The purpose of the present study was to assess safety and tolerability of carvedilol in CHF-patients. METHODS: 66 general practitioners, who were supervised by a local cardiologist, enrolled 151 CHF-patients. All patients were on standard therapy with ACE-inhibitors and diuretics. Carvedilol treatment was started with 3.125 mg twice daily and slowly uptitrated in 2-week intervals to 2x25 mg per day. Mean follow-up was 12 weeks. RESULTS: 145 of the 151 patients (96%) finished the study according to protocol, six patients were lost to follow-up (4%). 59 patients (41%) experienced minor and nine (6%) serious adverse events. 68 were under maximal therapy with 50 mg daily, 33 received 25 mg, and 15 12.5 mg. Overall tolerability was good and NYHA-class fell significantly from 2.2 to 1.8 (P<0.001). Mean heart rate decreased from 78 to 69 bpm (P<0.001), mean systolic blood pressure from 137 to 132 mmHg (P<0.001) and mean diastolic blood pressure from 80 to 76 mmHg (P<0.001). Quality of life significantly improved under carvedilol with a reduction in the Minnesota living with heart failure score from 1.28 to 0.88 (P<0.001). CONCLUSIONS: Carvedilol is well tolerated in CHF-patients treated by general practitioners. Serious adverse events and hospitalisations are rare. Thus, carvedilol is a safe drug in the treatment of CHF-patients and can be easily initiated and managed by the general practitioner.

Low-dose carvedilol improves left ventricular function and reduces cardiovascular hospitalization in Japanese patients with chronic heart failure: the Multicenter Carvedilol Heart Failure Dose Assessment (MUCHA) trial.

BACKGROUND: The efficacy and optimum dose of beta-blockers have not been established in Japanese patients with chronic heart failure (CHF). The efficacy and safety of two doses of carvedilol, a beta-blocker with vasodilator and antioxidant actions, were investigated in Japanese patients with CHF. METHODS: After screening and a carvedilol challenge phase, 174 patients with mild to moderate CHF were randomly assigned (double-blinded) to placebo, 2.5 mg of carvedilol twice daily, or 10 mg of carvedilol twice daily. After a 2- to 4-week uptitration phase, maintenance treatment was continued for 24 to 48 weeks. The primary end point was improvement of the global assessment of CHF by the attending physician. Secondary end points were death or hospitalization for cardiovascular disease, cardiovascular hospitalization, hospitalization for heart failure, change of left ventricular ejection fraction, and change in New York Heart Association class. RESULTS: Carvedilol therapy achieved dose-dependent improvement of all end points (P for linear trend, range.002 to <.001). Both carvedilol groups showed marked risk reduction (71% to 91%) for cardiovascular and CHF hospitalization and for death or cardiovascular hospitalization (P range,.024 to <.001 for pairwise comparisons with placebo). No significant differences were observed for noncardiovascular hospitalization or adverse events. CONCLUSIONS: In Japanese patients with mild or moderate CHF, carvedilol achieved dose-related improvement of CHF and left ventricular ejection fraction; cardiovascular hospitalization was markedly reduced. At 5 mg/d, carvedilol conferred an important patient benefit, less than at 20 mg/d.

Assessment of the efficacy of esmolol on the haemodynamic changes induced by laryngoscopy and tracheal intubation: a meta-analysis.

BACKGROUND: Adrenergic stress response induced by laryngoscopy and tracheal intubation (LTI) appears to be attenuated by esmolol, but its potential clinical benefits have not been fully weighed against possible adverse effects. METHODS: A systematic search up to May 2000 was performed using MEDLINE, EMBASE, LILACS, Cochrane library, manual searching and bibliographies in all languages. All randomised comparisons of esmolol with placebo on the haemodynamic changes elicited by LTI were obtained. Trials were included in the present meta-analysis if they recorded heart rate (HR), systolic pressure (SBP), mean arterial pressure (MAP) or diastolic pressure (DBP) at three different stages: pre-induction, immediately prior to intubation, and in the post-intubation period. Weighted mean differences (WMD) and 95% confidence intervals (CI) of the changes in the haemodynamic variables between treatment and placebo groups were calculated. RESULTS: Of 72 publications identified, 38 randomised controlled trials containing a total of 2009 patients were finally included. Eleven different regimens and doses of esmolol demonstrated effectiveness in the attenuation of HR and BP after LTI in a dose-dependent manner. The most effective regimen was a loading dose of 500 microg x kg(-1) x min(-1) over 4 min followed by continuous infusion dose of 200-300 microg x kg(-1) x min(-1) [WMD: 20.2 bpm (95% CI: 15.6 to 24.7)]. High bolus dose (200 mg) of esmolol produced a considerable decrease in DBP [WMD 10.1 mmHg (95% CI: 7.3 to 12.8)]. CONCLUSION: Esmolol is effective, in a dose-dependent manner, in the attenuation of the adrenergic response to LTI. To minimise its adverse effects it should be administered, when considered clinically appropriate, as a continuous infusion regimen.

Functional assessment of beta adrenoceptor subtypes in human colonic circular and longitudinal (taenia coli) smooth muscle.

BACKGROUND AND AIMS: The subtype and species related heterogeneity of beta adrenoceptors prompted a functional reappraisal of these molecular targets of motility inhibition in the human colon. METHODS: Relaxation of muscle strips was measured in vitro. RESULTS: The following agonists had decreasing relaxing potency (effective concentration range 10(-8)-10(-4) mol/l): (-)isoprenaline (non-selective), terbutaline (beta(2) selective), CGP 12177 (beta(3) selective, also beta(1), beta(2) antagonist), and SR 58611A (beta(3) selective). Isoprenaline and terbutaline were more potent on circular than taenia strips; CGP 12177 and SR 58611A weakly and partially relaxed taenia but had little effect on circular strips. The potency of isoprenaline on circular strips was greatly reduced by the beta(1) selective antagonist CGP 20712 (10(-7) mol/l), and less so by ICI 118551 (10(-7) mol/l, beta(2) selective). CGP 20712 and ICI 118551 together (both 3 x 10(-6) mol/l) had no effect on taenia relaxation by SR 58611A and rendered isoprenaline and terbutaline virtually inactive on circular strips, although not on taenia, which was relaxed at higher than control concentrations and maximally by isoprenaline. Propranolol, a beta(1), beta(2) non-selective antagonist, at high concentrations (10(-5) mol/l) prevented taenia relaxation by CGP 12177 and SR 58611A; its quantitative antagonism of isoprenaline (in common with that of CGP 12177 used as an antagonist) was competitive in circular strips but not on taenia. CONCLUSIONS: beta(1), beta(2), and beta(3) adrenoceptors are functionally detectable in the human colon; agonist stimulation of any one type relaxed taenia but only isoprenaline was fully effective at the beta(3) subtype.

Quantitative assessment of alterations in regional left ventricular contractility with color-coded tissue Doppler echocardiography. Comparison with sonomicrometry and pressure-volume relations.

BACKGROUND: Tissue Doppler imaging (TDI) is a novel method of color-coding myocardial velocity on-line. The objective of the present study was to evaluate endocardial velocity with TDI as a method of objectively quantifying alterations in regional contractility over a wide range induced by inotropic modulation. METHODS AND RESULTS: Myocardial length crystals were used to simultaneously assess regional left ventricular (LV) function, and high-fidelity pressure and conductance catheters were used to assess global LV contractility by pressure-volume relations in nine open-chest dogs. Mid-LV M-mode and two-dimensional color TDI images were recorded during control and inotropic modulation stages with dobutamine and esmolol. Predicted significant increases in TDI indices occurred with dobutamine: peak systolic velocity of 4.41 +/- 1.07 to 6.67 +/- 1.07 cm/s*, systolic time-velocity integral (TVI) of 0.43 +/- 0.12 to 0.62 +/- 0.10 cm*, and diastolic TVI of 0.49 +/- 0.11 to 0.71 +/- 0.17 cm*. Opposing significant decreases occurred with esmolol: peak systolic velocity of 4.46 +/- 0.94 to 2.31 +/- 0.81 cm/s*, systolic TVI of 0.47 +/- 0.12 to 0.19 +/- 0.11 cm*, and diastolic TVI of 0.55 +/- 0.11 to 0.33 +/- 0.11 cm* (*all P < .001 versus control). Changes in TDI peak systolic velocity were correlated with changes in fractional shortening (r = .88) and shortening velocity (r = .87) by sonomicrometry. Changes in TDI peak velocity from multiple mid-LV sites also correlated significantly with maximal elastance (r = .85 +/- .04) from pressure-volume relations. CONCLUSIONS: TDI measures reflect directional and incremental alterations in regional and global LV contractility and have the potential to quantify regional LV function.

Assessment of beta 2- and beta 3-adrenoceptors in rat white adipose tissues by radioligand binding assay.

We investigated the characteristics of beta-adrenoceptors (beta-ARs) in rat white adipose tissues (WAT) with a radioligand receptor binding assay using (-)-[3H]-CGP12177. Scatchard analysis revealed that there are high- and low-affinity sites for (-)-[3H]-CGP12177 in WAT. The (-)-[3H]-CGP12177 bound to a high-affinity site was displaced by 1 microM propranolol. The rank of pKi values of catecholamines for the site was isoproterenol > epinephrine > norepinephrine. By contrast, BRL37344A, BRL35135A and SR59230A, beta 3-selective agonists had high affinity for the low-affinity site of (-)-[3H]-CGP12177, whereas (-)-[3H]-CGP12177 bound to a low-affinity site was completely displaced by 100 microM bupranolol but not 1 microM propranolol. The pKi values of the catecholamines (isoproterenol, norepinephrine, epinephrine) for this site were very low. In addition, the correlation between the pKi values of various beta-agonists for the low-affinity site of rat WAT and those obtained from rat cloned beta 3-ARs was significant, but those of human cloned beta 3-ARs were not. Consequently, the results suggested that the high- and low-affinity sites were beta 2-ARs and beta 3-ARs in rat WAT, respectively.

Assessment of frequency dependency of the class III effects of almokalant: a study using programmed stimulation and recording of monophasic action potentials and ventricular paced QT intervals.

The aim of the present study was to assess the frequency dependency of the effects of almokalant, a selective class III antiarrhythmic drug, on ventricular repolarization using recordings of monophasic action potentials and measurements of ventricular paced QT intervals. Twenty male volunteers were studied during almokalant infusion aiming at plasma concentrations (Cpl) of 20, 50, 100, and 150 nmol/l. The duration of monophasic action potential at 90% repolarization (MAPD) was measured during incremental and premature ventricular extrastimulation. The ventricular paced QT interval was measured during incremental stimulation from the apical region (RV APEX) and the outflow tract (RVOT) of the right ventricle, and the frequency dependence was analyzed using a linear regression model. At an almokalant dose of Cpl > or = 50, there was a significant prolongation of the MAPD of 10-15%. The prolongation was of equal magnitude at all paced cycle lengths (CL). The MAPD of ventricular extrasystole increased in parallel over the range of coupling intervals studied and was significantly prolonged at Cpl 100 and 150. The ratio between the MAPD of the extrasystoles and preceding beats was unaltered after almokalant infusion. The ventricular paced QT intervals increased during almokalant infusion in a similar manner as that of the MAPD. During RV APEX stimulation, the prolongation was more pronounced at low heart rates, an effect that was not seen during RV OT stimulation. Almokalant significantly prolonged the MAPD at dose levels Cpl > or = 50. There was no evidence of a frequency dependence of this effect. The ventricular paced QT intervals were prolonged in a similar manner as that of the MAPD, and this effect exhibited a small reverse frequency dependence during RV APEX stimulation.

In situ assessment of the role of the beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow in human subcutaneous adipose tissue.

1. The involvement of beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow was investigated in abdominal subcutaneous adipose tissue of healthy young adults by use of an in situ microdialysis technique. 2. Dialysis probes were infused either with isoprenaline (non-selective beta-adrenoceptor agonist), CGP 12,177 (selective beta 3-adrenoceptor agonist having beta 1-/beta 2-antagonist properties), dobutamine (selective beta 1-adrenoceptor agonist) or terbutaline (selective beta 2-adrenoceptor agonist). The recovery of each probe used for perfusion was calculated by an in vivo calibration method. The local blood flow was estimated through the measurement of the escape of ethanol infused simultaneously with the drugs included in the probe. 3. Isoprenaline infusion at 0.01 microM had a weak effect while higher concentrations of isoprenaline (0.1 and 1 microM) caused a rapid, sustained and concentration-dependent increase of glycerol outflow; the maximum increase was 306 +/- 34% with 1 microM. Isoprenaline also increased the nutritive blood flow in adipose tissue; a significant effect appeared at 0.1 microM isoprenaline and was greater at 1 microM. 4. CGP 12,177 (10 and 100 microM) increased the glycerol concentration in the dialysate (128 +/- 8 and 149 +/- 12%, respectively) and nutritive blood flow. Terbutaline and dobutamine (100 microM) both provoked rapid and similar increases in glycerol outflow (252 +/- 18 and 249 +/- 18%, respectively). Both, terbutaline and dobutamine increased nutritive blood flow. 5. It is concluded that beta 1- and beta 2-adrenoceptor subtypes are both mainly involved in the mobilization of lipids and in the control of nutritive blood flow. beta 3-Adrenoceptors play a weaker role in the control of lipolysis and nutritive blood flow in human subcutaneous abdominal adipose tissue.

Assessment of beta-adrenergic receptor blockade after isamoltane, a 5-HT1-receptor active compound, in healthy volunteers.

This study investigated the effects of isamoltane on the changes induced by cumulative doses of inhaled albuterol (salbutamol) on bronchomotor tone, skeletal muscle, circulatory system, and metabolism after single (day 1) and multiple dosing (day 7) in 15 healthy subjects. The volunteers were given placebo, 4 mg isamoltane, 10 mg isamoltane, or 20 mg propranolol over a 7-day period in a randomized, double-blind, crossover design. The greatest attenuation in albuterol-induced beta-adrenergic receptor responses occurred with propranolol. The median provocative dose of albuterol causing a 50% increase in specific airway conductance was 337 and 315 micrograms (day 1 and day 7, respectively) for placebo, 336 and 322 micrograms for 4 mg isamoltane, 344 and 389 micrograms for 10 mg isamoltane, and 667 and 652 micrograms for propranolol. The provocative dose of albuterol producing a 35% increase in tremor was 464 and 539 micrograms (day 1 and day 7, respectively) for placebo, 1122 and 1270 micrograms for 4 mg isamoltane, 1612 and > 1612 micrograms for 10 mg isamoltane, and > 1612 and > 1612 micrograms for propranolol. On day 5 of each period an exercise test was performed. Propranolol reduced exercise heart rate by 11% (compared with placebo), 10 mg isamoltane reduced heart rate by 5%, and 4 mg isamoltane reduced heart rate by 1%. In conclusion, low-dose isamoltane caused measurable systemic effects on both beta 2- and beta 1-adrenergic receptors, and the dose-dependent blockade on beta 2-receptors of skeletal muscle was more clear than the attenuation of exercise heart rate.