Coadministration Of Propranolol Research Articles

Blockade of beta-adrenergic receptors reduces cancer growth and enhances the response to anti-CTLA4 therapy by modulating the tumor microenvironment

The development of immune checkpoint inhibitors (ICI) marks an important breakthrough of cancer therapies in the past years. However, only a limited fraction of patients benefit from such treatments, prompting the search for immune modulating agents that can improve the therapeutic efficacy. The nonselective beta blocker, propranolol, which for decades has been prescribed for the treatment of cardiovascular conditions, has recently been used successfully to treat metastatic angiosarcoma. These results have led to an orphan drug designation by the European Medicines Agency for the treatment of soft tissue sarcomas. The anti-tumor effects of propranolol are suggested to involve the reduction of cancer cell proliferation as well as angiogenesis. Here, we show that oral administration of propranolol delays tumor progression of MCA205 fibrosarcoma model and MC38 colon cancer model and increases the survival rate of tumor bearing mice. Propranolol works by reducing tumor angiogenesis and facilitating an anti-tumoral microenvironment with increased T cell infiltration and reduced infiltration of myeloid-derived suppressor cells (MDSCs). Using T cell deficient mice, we demonstrate that the full anti-tumor effect of propranolol requires the presence of T cells. Flow cytometry-based analysis and RNA sequencing of FACS-sorted cells show that propranolol treatment leads to an upregulation of PD-L1 on tumor associated macrophages (TAMs) and changes in their chemokine expression profile. Lastly, we observe that the co-administration of propranolol significantly enhances the efficacy of anti-CTLA4 therapy. Our results identify propranolol as an immune modulating agent, which can improve immune checkpoint inhibitor therapies in soft tissue sarcoma patients and potentially in other cancers.

The role of vimentin, Connexin-43 proteins, and oxidative stress in the protective effect of propranolol against clozapine-induced myocarditis and apoptosis in rats

Clozapine (CLZ) represents an effective treatment for resistant schizophrenia. However, myocarditis, recently reported in about 66% of the psychiatric patients treated with CLZ, has raised concerns about its safety. β-blocking agents have shown to be helpful in the management of myocarditis. Moreover, Vimentin (VIM) and Connexin-43 (CX43) are important structural proteins play key roles in cytoskeletal functions and cellular communication and have complex implications in pathophysiology. The present work aimed to study the mechanisms behind the protective effect of propranolol (PRO) against CLZ-induced myocarditis and the possible involvement of VIM and CX43. The effect of PRO (5 and 10 mg/kg, oral) on the myocarditis induced by CLZ (25 mg/kg/d, i. p.) treatment for 21 days in rats, was assessed biochemically, and immunohistochemically. CLZ treatment increased the serum levels of cardiac injury (CK-MP, LDH and cTn-I) and cardiac levels of oxidative stress (TBARS and NO) markers, proinflammatory cytokines (IL-1β and TNF-α), and mRNA expression of VIM and CX43 with decreased the antioxidant defenses (GSH and GSH-Px). Immunohistochemical study showed increased cardiac expression of VIM, CX43 and caspase-3 proteins. Coadministration of PRO with CLZ, dose-dependently decreased the biochemical and immunohistochemical hallmarks of CLZ-induced myocardial injury and significantly decreased mRNA expression of VIM and CX43. Taken together, our results demonstrate that the cardioprotective effects of PRO on CLZ-induced myocarditis are related in addition to its β-blocking activity to protection of myocardial VIM and CX43 proteins through antagonizing the CLZ-induced oxidative stress and inflammatory response, and preventing cell apoptosis.

51 Oxandrolone and Propranolol Coadministration Reduce Skeletal Muscle Amino Acid Transporters Expression in Children with Burns

51 Oxandrolone and Propranolol Coadministration Reduce Skeletal Muscle Amino Acid Transporters Expression in Children with Burns

Anti-inflammatory effects of propranolol in the temporomandibular joint of female rats and its contribution to antinociceptive action.

β-Blockers reduce temporomandibular joint (TMJ) pain. We asked whether they also reduce TMJ inflammation and, if so, whether this anti-inflammatory effect contributes to its analgesic action. We measured many parameters of the inflammatory response after co-administration of the β-blocker propranolol with the inflammatory agent carrageenan in the TMJ of female rats. We also hypothesized that the activation of β-adrenoceptors in the TMJ induces nociception mediated, at least in part, by the inflammatory response. To test this hypothesis, we examined the nociceptive response induced by the activation of the β-adrenoceptors in the TMJ in female rats pretreated with thalidomide and fucoidan. We found that the co-administration of propranolol with carrageenan in the TMJ of female rats significantly reduced several parameters of the inflammatory response induced by carrageenan such as plasma extravasation, neutrophil migration and the release of the pro-inflammatory cytokines TNF-α, IL-1β and CINC-1. Furthermore, the injection of the β-adrenergic receptor agonist isoproterenol in the TMJ induced nociception that was significantly reduced by thalidomide, fucoidan and by the co-administration of propranolol but not of the α-adrenergic receptor antagonist phentolamine. Propranolol has anti-inflammatory effects that contribute to its antinociceptive action in the TMJ of females. β-Blockers have an anti-inflammatory effect on temporomandibular joint (TMJ) that contributes to its analgesic effect. The results of this work suggest that β-blockers can be used to treat the painful conditions of TMJ, especially when they are associated with an inflammatory process.

Effects of salbutamol on the inflammatory parameters and angiogenesis in the rat air pouch model of inflammation.

In the present study, effects of salbutamol on the inflammatory parameters, angiogenesis, interleukin-1 beta (IL-1β) and vascular endothelial growth factor (VEGF) levels were investigated in an air pouch model of inflammation. Inflammation was induced by intrapouch administration of 1% solution of sterile carrageenan in male Wistar rats. Salbutamol (125, 250 and 500 µg/rat) and salbutamol (500 µg/rat) plus propranolol (100 μg/rat) were injected intrapouch. After 6 and 72 h, fluid inside the pouches was collected to measure volume of exudates, leukocytes number and IL-1β levels. To determine angiogenesis, the granulation tissues were dissected out and weighed 3 days after carrageenan injection, then hemoglobin concentration was assessed using a hemoglobin assay kit. In addition, amount of VEGF in the exudates was measured 72 h after induction of inflammation. Leukocyte accumulation and the volume of exudates were significantly inhibited by salbutamol administration. In addition, salbutamol decreased the production of VEGF and IL-1β. Moreover, all used doses of salbutamol significantly inhibited angiogenesis. Interestingly, effects of salbutamol on the attenuation of angiogenesis and inflammatory parameters was similar to diclofenac sodium. Co-administration of propranolol with salbutamol clearly reversed anti-inflammatory effects of salbutamol. Salbutamol can decrease acute and chronic inflammation by β2-adrenergic receptors activation. The observed IL-1β and VEGF inhibitory properties of salbutamol may be responsible for anti-inflammatory and anti-angiogenic effect of the agent.

Propranolol and oxytocin versus oxytocin alone for induction and augmentation of labor: a meta-analysis of randomized trials.

We sought to study the effect of propranolol co-administration with oxytocin during the latent and active phases of labor on labor outcomes. We searched Medline, Scopus, ClinicalTrials.gov and Cochrane Central Register databases. The meta-analysis was performed with the RevMan 5.1 software. Six studies were included in the present meta-analysis which enrolled 609 parturient. According to the findings of our study, propranolol administration during the latent phase effectively reduces the cesarean section rates (OR 0.49, 95 % CI 0.27, 0.89). However, this beneficial effect is not observed during the active phase of labor. The 5 min neonatal Apgar scores are not influenced by its administration (MD -0.07, 95 % CI -0.017, 0.02). Respectively, the neonatal admissions to a NICU are similar to those of neonates exposed only to oxytocin (OR 0.96, 95 % CI 0.36, 2.53). Propranolol's effect on the duration of the various stages of labor was underreported, however, evidence seem to support that it shortens the latent phase and possibly the total duration of labor. Firm results are, however, precluded due to the low number enrolled parturient and due to the significant methodological heterogeneity of included studies.

Pharmacokinetic and pharmacodynamic interaction of siponimod (BAF312) and propranolol in healthy subjects.

To evaluate the cardiac and pulmonary effects of siponimod (BAF312) and propranolol co-administration in healthy subjects. Healthy subjects (n=76) were randomized in a doubleblind manner to receive propranolol at siponimod steady state (group A), siponimod at propranolol steady state (group B), placebo (group C) and propranolol (group D). Pharmacodynamic evaluations included maximum change from baseline in time-matched hourly average heart rate (Emax HR) and mean arterial blood pressure (Emax MABP) over 24 hours postdose, change from baseline in PR intervals, cardiac rhythm, and forced expiratory volume in 1 second (FEV1). Pharmacokinetic and safety parameters were also assessed. Siponimod and propranolol when administered alone resulted in similar HR decrease at steady state. Compared to propranolol alone, the combination at steady state had an additional 6.21 bpm (95%CI: 2.32, 10.11) decrease of mean EmaxHR, a decrease of 5.04 bpm (0.52, 9.56) for group A and 7.39 bpm (2.87, 11.90) for group B. A minor decrease in MABP and a trend towards PR interval increase were noted with co-administration treatment vs. propranolol alone. There were no episodes of second-degree atrioventricular blocks or sinus pauses>3 seconds. Baseline-corrected FEV1 was reduced by -0.07 L (95% CI: -0.17, 0.03) for group A and -0.05 L (-0.15, 0.05) for group B vs. propranolol alone. There were no cardiovascular adverse events during coadministration treatment. Coadministration of siponimod and propranolol was well tolerated. Bradyarrhythmic effects were less pronounced when propranolol was added to siponimod steady-state therapy compared with siponimod addition to propranolol.

Effects of the beta-adrenergic receptor antagonist Propranolol on dyskinesia and L-DOPA-induced striatal DA efflux in the hemi-parkinsonian rat.

Dopamine (DA) replacement therapy with L-DOPA continues to be the primary treatment of Parkinson's disease; however, long-term therapy is accompanied by L-DOPA-induced dyskinesias (LID). Several experimental and clinical studies have established that Propranolol, a β-adrenergic receptor antagonist, reduces LID without affecting L-DOPA's efficacy. However, the exact mechanisms underlying these effects remain to be elucidated. The aim of this study was to evaluate the anti-dyskinetic profile of Propranolol against a panel of DA replacement strategies, as well as elucidate the underlying neurochemical mechanisms. Results indicated that Propranolol, in a dose-dependent manner, reduced LID, without affecting motor performance. Propranolol failed to alter dyskinesia produced by the D1 receptor agonist, SKF81297 (0.08 mg/kg, sc), or the D2 receptor agonist, Quinpirole (0.05 mg/kg, sc). These findings suggested a pre-synaptic mechanism for Propranolol's anti-dyskinetic effects, possibly through modulating L-DOPA-mediated DA efflux. To evaluate this possibility, microdialysis studies were carried out in the DA-lesioned striatum of dyskinetic rats and results indicated that co-administration of Propranolol (20 mg/kg, ip) was able to attenuate L-DOPA- (6 mg/kg, sc) induced DA efflux. Therefore, Propranolol's anti-dyskinetic properties appear to be mediated via attenuation of L-DOPA-induced extraphysiological efflux of DA.

Effect of coadministration of propranolol and etodolac (VT-122) plus sorafenib for patients with advanced hepatocellular carcinoma (HCC).

390 Background: Propranolol and etodolac (designated VT-122) target the adrenergic and prostaglandin stress systems activated in HCC. These stress-induced systems are proposed to induce changes in the tumor microenvironment and immune system leading to tumor promotion and immune tolerance. In a separate study, administration of VT-122 prior to sorafenib showed an increase in median overall survival (OS) of 21 months when VT-122 is administered before sorafenib compared to 10 months OS for sorafenib alone. The aim of the current study was to evaluate the effect of administering VT-122 at least 30 days after starting sorafenib. Methods: Patients with HCC receiving sorafenib for at least 30 days were eligible for this double-blind, placebo-controlled study. Patients were randomized to receive sorafenib with either VT-122 or placebo. Patients received therapy for up to 12 months or until treatment failure. VT-122 was administered twice daily. The primary endpoint was duration of therapy (DoT) and the secondary endpoint was OS. Results: Twenty patients were randomized, 11 and 9 patients to the VT122 and placebo arm, respectively. Each arm was balanced with regards to age (mean of 60.4 years), Child Pugh status (9 Child Pugh A, 11 Child Pugh B7), hepatitis virus status (6 HBV and 1 HCV positive) and C-reactive protein (CRP) (20.4 mg/L). VT122 with sorafenib was well tolerated with no unexpected serious adverse events reported. Mean OS was 13.9 months and 9.6 months in the VT-122 and placebo arms, respectively. Mean DoT (unvalidated) was 10.1 months and 7.5 months in the VT-122 and placebo arms, respectively. Conclusions: Co-administration of VT-122 with sorafenib was well tolerated and showed an increase in duration of therapy and OS versus sorafenib alone. The small sample size and number of events precludes the ability to make any significant efficacy conclusions. The increase in survival was not as great as that seen in a separate study in which VT122 was started prior to sorafenib. A further Phase 3 study of VT122 administered prior to sorafenib in patients with HCC is warranted. Clinical trial information: NCT01265576.

Neuropeptide S interacts with the basolateral amygdala noradrenergic system in facilitating object recognition memory consolidation

The noradrenergic activity in the basolateral amygdala (BLA) was reported to be involved in the regulation of object recognition memory. As the BLA expresses high density of receptors for Neuropeptide S (NPS), we investigated whether the BLA is involved in mediating NPS’s effects on object recognition memory consolidation and whether such effects require noradrenergic activity. Intracerebroventricular infusion of NPS (1nmol) post training facilitated 24-h memory in a mouse novel object recognition task. The memory-enhancing effect of NPS could be blocked by the β-adrenoceptor antagonist propranolol. Furthermore, post-training intra-BLA infusions of NPS (0.5nmol/side) improved 24-h memory for objects, which was impaired by co-administration of propranolol (0.5μg/side). Taken together, these results indicate that NPS interacts with the BLA noradrenergic system in improving object recognition memory during consolidation.

Interaction between morphine and noradrenergic system of basolateral amygdala on anxiety and memory in the elevated plus-maze test based on a test-retest paradigm.

The amygdala is the key brain structure for anxiety and emotional memory storage. We examined the involvement of β-adrenoreceptors in the basolateral amygdala (BLA) and their interaction with morphine in modulating these behaviors. The elevated plus-maze has been employed for investigating anxiety and memory. Male Wistar rats were used for this test. We injected morphine (4, 5, and 6 mg/kg) intraperitoneally, while salbutamol (albuterol) (1, 2, and 4 μg/rat) and propranolol (1, 2, and 4 μg/rat) were injected into the BLA. Open- arms time percentage (%OAT), open- arms entry percentage (%OAE), and locomotor activity were determined by this behavioral test. Retention was tested 24 hours later. Intraperitoneal injection of morphine (6 mg/kg) had an anxiolytic-like effect and improvement of memory. The highest dose of salbutamol decreased the anxiety parameters in test session and improved the memory in retest session. Coadministration of salbutamol and ineffective dose of morphine presenting anxiolytic response. In this case, the memory was improved. Intra-BLA administration of propranolol (4 μg/rat) decreased %OAT in the test session, while had no effect on memory formation. Coadministration of propranolol and morphine (6 mg/kg) showed an increase in %OAT. There was not any significant change in the above- mentioned parameter in the retest session. Coadministration of morphine and propranolol with the effective dose of salbutamol showed that propranolol could reverse anxiolytic-like effect. We found that opioidergic and β-adrenergic systems have the same effects on anxiety and memory in the BLA; but these effects are independent of each other.

Lidocaine for prolonged and intensified spinal anesthesia by coadministration of propranolol in the rat

Although the coadministration of lidocaine with propranolol interferes with the metabolic profile (pharmacokinetics), its pharmacodynamics is still unclear. In this report, we investigate whether propranolol can potentiate the effect of lidocaine. Rats received spinal anesthesia with lidocaine co-injected with propranolol. After intrathecal injections of drugs in rats, three neurobehavioral examinations (motor function, proprioception, and nociception) were performed. We showed that lidocaine and propranolol elicited a spinal blockade in motor function, proprioception, and nociception. Propranolol at the dose of 0.82μmol/kg produced no spinal anesthesia. Co-administration of lidocaine [50% effective dose (ED50) or ED95] and propranolol (0.82μmol/kg) produced greater spinal anesthesia than lidocaine (ED50 or ED95), respectively. These preclinical findings demonstrated that propranolol and lidocaine displayed spinal anesthesia. When combined with propranolol, lidocaine elicited a supra-additive effect of spinal anesthesia.

Intrathecal propranolol displays long-acting spinal anesthesia with a more sensory-selective action over motor blockade in rats

To prevent cardiovascular effects of peripherally administered propranolol, the aim of this study was to evaluate the spinal anesthetic effect of propranolol, a Na ± channel blocker. After rats were injected with drugs intrathecally, the spinal anesthetic effect of propranolol was compared with that of lidocaine, which is known to produce local anesthesia. We also evaluated the effect of the addition of clonidine with propranolol on spinal anesthesia. Our results showed that propranolol produced a dose-dependent spinal blockade in motor, proprioception, and nociception. On a 50% effective dose (ED 50) basis, the spinal anesthetic effect of propranolol in motor, proprioception, and nociception [1.16 (1.01–1.34), 1.10 (0.92–1.31), 1.05 (0.89–1.24)] was equal to lidocaine [1.03 (0.94–1.13), 0.95 (0.84–1.07), 0.87 (0.79–0.96)], respectively. On an equipotent basis (0.5, 1.0, 2.5 μmol), the sensory/nociceptive block duration caused by propranolol was longer than that caused by lidocaine (P ≤ 0.01). Co-administration of propranolol (1.1 μmol) and clonidine (0.5 μmol) produced greater spinal anesthesia than propranolol (1.1 μmol) or clonidine (0.5 μmol) alone. These preclinical findings demonstrated that propranolol produces similar spinal anesthesia to lidocaine and that α 2-adrenergic receptors also contribute to improve the quality and duration of the spinal anesthetic effect of propranolol. Propranolol with a more sensory-selective action over motor blockade elicited longer spinal blockade than did lidocaine.

Stimulation of Renin Secretion by Angiotensin II Blockade is Gsα-Dependent

Angiotensin II converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB) presumably stimulate renin secretion by interrupting angiotensin II feedback inhibition. The increase in cytosolic calcium caused by activation of Gq-coupled AT1 receptors may mediate the renin-inhibitory effect of angiotensin II at the cellular level, implying that ACEI and ARB may work by reducing intracellular calcium. Here, we investigated whether angiotensin II blockade acts predominantly through Gs-mediated stimulation of adenylyl cyclase (AC) by testing the effect of ACEI and ARB in mice with juxtaglomerular cell-specific deficiency of the AC-stimulatory Gsalpha. The ACEI captopril and quinaprilate and the ARB candesartan significantly increased plasma renin concentration (PRC) to 20 to 40 times basal PRC in wild-type mice but did not significantly alter PRC in Gsalpha-deficient mice. Captopril also completely abrogated renin stimulation in wild-type mice after co-administration of propranolol, indomethacin, and L-NAME. Treatment with enalapril and a low-NaCl diet for 7 days led to a 35-fold increase in PRC among wild-type mice but no significant change in PRC among Gsalpha-deficient mice. Three different pharmacologic inhibitors of AC reduced the stimulatory effect of captopril by 70% to 80%. In conclusion, blockade of angiotensin II stimulates renin synthesis and release indirectly through the action of ligands that activate the cAMP/PKA pathway in a Gsalpha-dependent fashion, including catecholamines, prostaglandins, and nitric oxide.

P-Glycoprotein (Abcb1) is involved in absorptive drug transport in skin

The purpose of the present study was to investigate the role of P-glycoprotein (P-gp) in drug disposition in skin. The distribution of P-gp substrates (rhodamine 123 and itraconazole) to the skin after administration from the epidermal side was lower in P-gp gene knockout ( mdr1a/1b −/− ) mice than that in wild-type mice. Coadministration of propranolol, a P-gp inhibitor, decreased the distribution of itraconazole to the skin in wild-type mice, but not in mdr1a/1b −/− mice. These results suggest that P-gp contributes to the influx (from the epidermal side) of its substrates into skin, although P-gp is generally involved in efflux of drugs from various tissues. This finding was supported by the lower vectorial transport of rhodamine 123 from the epidermal to the hypodermal side in mdr1a/1b −/− mice in Ussing-type chamber experiments and by the immunohistochemical localization of P-gp throughout the dermal layer. Distribution of itraconazole after intravenous administration, on the other hand, was higher in mdr1a/1b −/− mice than that in wild-type mice, suggesting that P-gp transports this drug from the skin to the circulation. The present findings are the first to demonstrate involvement of P-gp in dermal drug disposition.

Morphine and propranolol co-administration impair consolidation of Y-maze spatial recognition memory

In the present study, the interaction between morphine and the beta-adrenergic receptor antagonist, propranolol (PROP), in memory consolidation was investigated in a two-trial recognition Y-maze task. Four sets of Y-maze experiments were carried out in mice, with 2 and 4 h inter-trial intervals (ITI) and all drugs administered immediately after the training trials. In the first and second sets of experiments, post-training administration of morphine (0.25 and 2.5 mg/kg) or PROP (2, 10 and 20 mg/kg) alone did not impair memory consolidation after a 2 h ITI. However, in the third and fourth sets of experiments, co-administration of these ineffective doses of morphine (0.25 and 2.5 mg/kg) and PROP (2, 10 and 20 mg/kg) disrupted memory consolidation after a 2 h ITI. Moreover, the relatively higher dose of morphine (2.5 mg/kg) plus the relatively higher doses of PROP (10 and 20 mg/kg) disrupted memory consolidation to a greater extent after a 2 h ITI. Locomotor activity was not affected by any of the drug treatments. Our data shows that morphine and PROP co-administration disrupts the consolidation of spatial recognition memory, suggesting that inactivation of the beta-adrenergic system may contribute to morphine-induced impairment of memory.

The beta‐adrenoceptor antagonist propranolol counteracts anti‐inflammatory effects of isoflurane in rat endotoxemia

Recent studies suggest that volatile anaesthetics have anti-inflammatory and preconditioning properties and that beta-adrenoceptors are involved in the signalling pathways for these effects. Concurrently, the blockade of beta-adrenoceptors has been shown to augment the release of inflammatory mediators in response to pro-inflammatory stimuli. We therefore aimed to investigate whether the beta-adrenoceptor antagonist propranolol might modulate the anti-inflammatory effects of isoflurane on the systemic and pulmonary release of pro-inflammatory cytokines in endotoxemic rats. Forty anaesthetized and ventilated Sprague-Dawley rats were randomly treated as follows. Lipopolysaccharide (LPS) only (n = 8), endotoxemia with LPS [5 mg/kg, intravenously (i.v.)]. LPS-isoflurane (n = 8): endotoxemia and continuous inhalation of 1 minimum alveolar concentration (MAC) of isoflurane. LPS-isoflurane-propranolol (n = 8): administration of propranolol (3 mg/kg) before continuous inhalation of isoflurane and induction of endotoxemia. LPS-propranolol (n = 8): administration of propranolol (3 mg/kg) before endotoxemia without inhalation of isoflurane. Sham (n = 8): control-group only with surgical preparation. After 4 h of endotoxemia, levels of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-10 (IL-10) in plasma and bronchoalveolar fluid (BALF) were analysed. Release of nitric oxide (NO) and amount of inducible nitric oxide synthase (iNOS) protein in alveolar macrophages was measured by Griess assay or determined by Western Blotting, respectively. Inhalation of isoflurane reduced the release of TNF-alpha (P < 0.05) and IL-1beta (P < 0.05) in plasma and IL-1beta (P < 0.05) in BALF. Co-administration of propranolol significantly inhibited these effects. During inhalation of isoflurane, the increased release of NO and iNOS protein from alveolar macrophages was also completely inhibited by propranolol. Our results indicate for the first time, that blockade of beta-adrenoceptors counteracts the anti-inflammatory effects of isoflurane in endotoxemic rats.

Protein phosphatase activity is increased in a rat model of long-term beta-adrenergic stimulation.

We tested the hypothesis that altered phosphorylation of Ca2+ regulatory proteins contributes to contractile anomalies in cardiac hypertrophy. Cardiac hypertrophy was induced in rats by chronic s.c. administration of isoproterenol (Iso, 2.4 mg/kg/day) via osmotic minipumps. On day 2 of Iso treatment the expression of atrial natriuretic factor was increased, time of relaxation in isolated papillary muscles shortened and protein expression of phospholamban (PLB) and sarcoplasmic reticulum Ca2+-ATPase reduced. In addition, the phosphorylation state of PLB at serine-16 and threonine-17 was decreased from (arbitrary units) 2.3+/-0.3 to 1.1+/-0.2 and from 4.1+/-0.6 to 2.1+/-0.2, respectively. This was not accompanied by altered activity of PLB-phosphorylating protein kinases (protein kinase A or Ca2+/calmodulin-dependent protein kinase II), whereas the activity of types 1 and 2A protein phosphatases (PP1 and -2A respectively) was enhanced from 1.1+/-0.08 to 1.71+/-0.13 nmol/mg/min. Iso treatment did not alter the PP1/PP2A activity ratio and 1 nmol/l okadaic acid, a concentration which completely blocks the catalytic subunit of PP2A, inhibited about 40% of total PP activity in all groups studied. These data indicate that the activity of both PP1 and PP2A were increased. All effects of Iso treatment were abolished by co-administration of propranolol (29.7 mg/kg/day). It is concluded that dephosphorylation of PLB is due to enhanced activity of PP1 and PP2A. We suggest that chronic beta-adrenergic stimulation, which occurs in human cardiac hypertrophy and failure, can lead to increased activity of PPs. This may contribute to altered contractile responses in the hypertrophied heart.

Muscle and serum changes with salbutamol administration in aerobically exercised rats

Treatment of experimental animals subjected to 90 days physical training programme plus repeated doses of salbutamol, a β-adrenergic agonist, administered under two different regimes: therapeutic (16 μg/kg body weight, twice a day) and doping (3 mg/kg body weight, twice a day), caused a marked increase in size of skeletal (soleus, gastrocnemius and plantaris) leg muscles. Adrenergic involvement of salbutamol-linked hypertrophy was demonstrated by co-administration of the non-specific β-adrenergic antagonist d, l-propranolol (10 mg/kg body weight twice a day). The salbutamol-induced muscle hypertrophy was associated with an early increase in creatine phosphokinase (CK) and its myocardial isozyme (CKmb), without significant changes in lactate dehydrogenase (LDH), alanine aminotransferase (AAT) and aspartate aminotransferase (DAT). The induction of muscle-injury biomarkers was completely abolished by co-administration of propranolol, thus suggesting the adrenergic involvement of these alterations.

Potential drug interactions with the novel antimigraine compound zolmitriptan (Zomig, 311C90).

Seven randomized studies in healthy volunteers have investigated interactions between zolmitriptan (Zomig, formerly 311C90), a 5HT1B/1D agonist for acute migraine therapy, and selected drugs with which there was a possibility of interaction or a likelihood of concurrent use. Co-administration of oral dihydroergotamine, ergotamine, pizotifen, fluoxetine, paracetamol (acetaminophen)/metoclopramide or selegiline had no clinically significant effects on the pharmacokinetics of zolmitriptan or its metabolites, although small changes were observed in some cases. Co-administration of propranolol resulted in a 56% increase in the area under the plasma concentration-time curve (AUC) of zolmitriptan and a 11% decrease in the AUC of the active metabolite 183C91. However, these pharmacokinetic changes are unlikely to be relevant at lower clinical doses. Moclobemide, a monoamine oxidase A (MAO-A) inhibitor, decreased the clearance of zolmitriptan and, in particular, 183C91. This suggests that MAO-A is involved in the metabolism of 183C91 and it may be prudent to limit the daily zolmitriptan dose in migraine patients maintained on a MAO-A inhibitor. The clinically insignificant blood pressure increases produced by zolmitriptan, and the tolerability profile of this agent, were unaffected by any of the concomitant medications. Clinically significant interactions between zolmitriptan and commonly co-prescribed antimigraine therapies are unlikely.