Prostaglandin E2 excitatory effects on rat urinary bladder: a comparison between the ß-adrenoceptor modulation of non-voiding activity in vivo and micro-contractile activity in vitro.

Prostaglandin E2 (PGE2) is well known to modulate urinary bladder functions, but it is also thought to be involved in the pathophysiology of lower urinary tract dysfunctions, since high levels of PGE2 have been found in overactive bladder (OAB) patients. ß-Adrenoceptors are major players in detrusor muscle relaxation, and the selective ß3-adrenoceptor (AR) agonist mirabegron was recently approved for the treatment of overactive bladder (OAB). ß-Adrenoceptor modulation of PGE2 excitatory effects on bladder detrusor muscle was investigated by i.v. mirabegron after intravesical PGE2 infusion in conscious rats. Non-voiding activity (NVA) was assessed under isovolumetric conditions. In addition, mirabegron and isoprenaline (0.01-10 µM) were studied on PGE2-increased micro-contractile activity during isometric tension recordings of intact isolated bladder muscle strips. Our investigations showed that PGE2 dramatically increased NVA in vivo and spontaneous micro-contractions in vitro. In vivo administration of mirabegron (0.1, 0.3 and 3 mg/kg) reduced PGE2-augmented NVA in dose-dependent manner, while the PGE2-increased micro-contractions in isolated bladder strips were poorly inhibited. Isoprenaline inhibited PGE2-augmented micro-contractions in a concentration-dependent manner and had a higher potency compared to mirabegron. The apparent pKB of 7.25 for metoprolol at the isoprenaline concentration-response curve for PGE2-augmented micro-contractions suggests a ß1-AR-mediated.

Beta adrenergic modulation of spontaneous microcontractions and electrical field-stimulated contractions in isolated strips of rat urinary bladder from normal animals and animals with partial bladder outflow obstruction.

Spontaneous microcontractions and electrical field stimulation (EFS)-evoked contractions in isolated rat bladder strips from normal and from 6 weeks partial bladder outflow obstruction (pBOO) animals were studied to identify the potential site of action for the ß3-adrenoceptor (AR) agonist mirabegron in detrusor overactivity in rats. For this, effects of the ß-AR agonist isoprenaline and mirabegron were tested in presence or absence of selective antagonists for ß-AR subtypes, namely CGP-20712A for ß1-AR, ICI-118,551 for ß2-AR, and L-748,337 for ß3-AR. In detrusor strips from both normal and obstructed animals, EFS-induced contractions were weakly affected by isoprenaline and even less so by mirabegron. In contrast, microcontraction activity was more potently reduced by isoprenaline (pIC50 7.3; Emax ±85 %), whereas mirabegron showed a small effect. In pBOO strips, concentration response curves for isoprenaline and mirabegron at inhibition of EFS and spontaneous microcontractions were similar to those in normal strips. Isoprenaline-induced inhibition of microcontractions and EFS was antagonized by the ß1-AR antagonist, but not by the ß2- and ß3-AR antagonists. In the context of ß3-AR-mediated bladder functions for mirabegron in other experiments, the current data question a role for effects at spontaneous microcontractions, or neurogenic detrusor stimulation in the mode of action for mirabegron in vivo, since functional bladder effects for mirabegron are reported to occur at much lower concentrations.

The characteristics of intrinsic complex micro-contractile activity in isolated strips of the rat bladder.

In the resting and un-stimulated state, the bladder wall is not quiescent and discrete contractile events, microcontractions, can be recorded in almost all species. This activity contributes to the active element of compliance and to the basal resting tension. This intrinsic activity underpins the more complex phasic activity, non-voiding activity (NVA) that can be seen to increase progressively as the bladder is filled. The NVA represents the motor component of a motor sensory system that relays information to the CNS on bladder volume. Despite the importance of this intrinsic motor activity, little is known about the mechanisms involved in its generation and modulation. The present experiments were done on isolated hemi-bladders from normal rats and measurements made of the intrinsic motor activity. Detailed analysis of the resting state reveals the presence of discrete phasic contractile events, micro-contractions that range in amplitude from 0.1-0.6 mN. These events seem to occur randomly and the basal activity has the appearance of 'noise'. An analysis of the frequency amplitude distribution of the contractile events, reveals that the total activity appears to be the sum of a number of discrete contractile units, each generating a phasic contraction about a specific mean value and with characteristic frequency. In a hemi-bladder, there are between 20-30 units generating the activity at rest. Using the timed integral of the activity (product of amplitude and frequency), it was noted that the activity was increased by the muscarinic agonist carbachol, but it was decreased by the ß-adrenergic agonist isoprenaline. Stretching the preparations also increased the activity. Using these observations, a simple model of the structural and functional organisation of the isolated rat bladder is proposed: the wall appears to be arranged into a number of discrete motor units acting independently. However, the activity can be stimulated or inhibited by pharmacological agents and mechanically (stretch). The possible relevance of this activity, its relationship to NVA and in relation to the mode of action of drugs are discussed. [Corrected]

How does the urothelium affect bladder function in health and disease? ICI-RS 2011.

The urothelium is a multifunctional tissue that not only acts as a barrier between the vesical contents of the lower urinary tract and the underlying tissues but also acts as a sensory organ by transducing physical and chemical stresses to the attendant afferent nervous system and underlying smooth muscle. This review will consider the nature of the stresses that the urothelium can transduce; the transmitters that mediate the transduction process; and how lower urinary pathologies, including overactive bladder syndrome, painful bladder syndrome and bacterial infections, are associated with alterations to this sensory system. In particular, the role of muscarinic receptors and the TRPV channels system will be discussed in this context. The urothelium also influences the contractile state of detrusor smooth muscle, both through modifying its contractility and the extent of spontaneous activity; potential pathways are discussed. The potential role that the urothelium may play in bladder underactivity is introduced, as well as potential biomarkers for the condition that may cross the urothelium to the urine. Finally, consideration is given to vesical administration of therapeutic agents that influence urinary tract function and how the properties of the urothelium may determine the effectiveness of this mode of delivery.

Voltage-dependent effects of barnidipine in rat vascular smooth muscle.

The effects of the dihydropyridine nifedipine and its more lipophilic congener, barnidipine, were investigated in smooth muscle preparations from the rat in resting and depolarizing conditions. Both drugs relaxed precontracted aortic rings more potently in depolarizing conditions, barnidipine being more potent than nifedipine. Currents through Ca2+ channels in rat vascular smooth muscle cells (A7r5) and in isolated rat cardiomyocytes were reduced more potently by both drugs at a holding potential of -40 mV than at -80 mV. However, barnidipine and nifedipine were more effective in reducing the current in A7r5 cells than in cardiomyocytes. The IC(50) obtained in aortic rings and in A7r5 cells were similar for barnidipine but an order of magnitude different for nifedipine. The results show that, in depolarizing conditions, barnidipine was more effective than nifedipine. It is suggested that the higher potency of barnidipine acting in vascular smooth muscle is related to both a higher affinity to the inactivated state of vascular Ca2+ channels and to a more lipophilic property as compared with nifedipine.

Barnidipine, a long-acting slow onset calcium antagonist.

Barnidipine is a stereochemically pure dihydropyridine calcium antagonist with a high potency. The drug showed a slow onset and long-lasting vasorelaxating effect in vitro, and strong antihypertensive activity in hypertension models. Barnidipine was shown to have a high vasoselectivity and offered protection in cardiac and renal ischaemia models. The in vitro drug:drug interaction profile suggests a low potential for clinically relevant interactions with concomitant medication. It can be anticipated that barnidipine is an attractive calcium antagonist, offering good blood pressure control without compensatory baroreflex activity.

BPS epilepsy joint symposium. 18 November 1999, London, UK.

This symposium, jointly organized by the British Pharmacological Society, the Pharmaceutical Sciences Group of the Royal Pharmaceutical Society and the National Society for Epilepsy, provided comprehensive information on anti-epileptic therapy and drug development issues. The spectrum of medical imaging techniques was evaluated for application in patient classification and diagnosis, therapeutic or surgical options, and for studying sites and mechanisms of drug action. The value of established therapeutics, as opposed to recent new drug interactions and therapeutics awaiting registration, were discussed in view of their clinical pharmacology, therapeutic use and drug-drug interaction properties. There were discussions on clinical drug testing problems in relation to trial design, and drug screening strategies from the perspective of perceived unmet clinical needs, such as refractory epilepsy and epileptogenesis. New developments, especially in the field of glutamate modulation, were reviewed for anti-epileptic drug potential. The conclusion was that in spite of progress, rational drug development of anti-epileptic drugs is still far away. Possible reasons for this could be that during drug screening, the focus is on drug properties in isolated rather than integrated neuronal circuits. In addition, there is a poor translation of drug effects in models for seizures and convulsions compared with epilepsy and epileptogenesis in man, and also the obstacle of rigidity in drug registration trials. It was a very valuable meeting for those who wanted to be informed about the frontiers and challenges in the development of anti-epileptic drugs.

In vitro investigation of the bladder-vascular selectivity of levcromakalim and YM934 in human tissues.

OBJECTIVE: To examine the potencies of the potassium-channel openers (KCOs) levcromakalim and YM934 as relaxing agents on human detrusor and human mesenteric artery smooth muscle, and to determine their bladder-vascular selectivity in vitro. MATERIALS AND METHODS: Strips of human detrusor muscle and mesenteric artery (with the endothelium removed) were set up in physiological salt solution and the tension developed by the tissues recorded. Tissues were precontracted with a concentration of carbachol (detrusor) or phenylephrine (artery) which caused 80% of maximal contraction, and relaxation responses to levcromakalim and YM934 were then obtained. RESULTS: Both KCOs caused relaxation of the bladder detrusor muscle and the mesenteric artery. Maximal responses, when plotted as a percentage of the precontraction, were greater for both KCOs in the bladder muscle than the artery, but the differences were small and not statistically significant. The sensitivity (drug potency) of the detrusor muscle to the KCOs was more than twice that of the artery but this selectivity was only statistically significant for YM934. CONCLUSIONS: Only minor bladder-vascular selectivity for levcromakalim and YM934 could be detected in vitro. This suggests that neither drug would be tolerated clinically, although the results suggest that further development of bladder-selective KCO agents appears feasible.

Relaxant effects of potassium-channel openers on normal and hyper-reflexic detrusor muscle.

OBJECTIVE: To compare the effects of the potassium-channel openers, levcromakalim and YM934, in isolated human detrusor muscle from normal and hyper-reflexic bladders. MATERIALS AND METHODS: Strips of human detrusor muscle from normal and hyper-reflexic bladder were pre-contracted with carbachol and the potassium-channel openers (0.1-0.3 mumol/L) were added cumulatively to the organ baths. Other strips were field-stimulated at frequencies producing 25% and 75% of the maximum response to field stimulation. Contractions could be abolished by atropine (10 mumol/L) and tetrodotoxin (1 mumol/L). RESULTS: The hyper-reflexic bladder was significantly more sensitive to carbachol than the normal bladder but the maximum response was significantly lower in the hyper-reflexic tissue. There was no significant difference between the potency of the potassium-channel openers in normal and hyper-reflexic detrusor muscle. Hyper-reflexic bladder was significantly more sensitive to electrical field stimulation than was normal bladder: maximum responses to field stimulation were not significantly different. Concentration-response curves for the potassium-channel openers were displaced to the left in hyper-reflexic bladder at both 25% and 75% maximum frequencies: however, only with levcromakalim at 75% of the maximum frequency was the shift significant. CONCLUSION: The greater sensitivity of hyper-reflexic bladder to carbachol and field stimulation supports existing evidence for post-junctional supersensitivity in detrusor instability. The results of this study also suggest that there are no appreciable changes in KATP channel function in the unstable bladder.

The effects of tamsulosin, a high affinity antagonist at functional alpha 1A- and alpha 1D-adrenoceptor subtypes.

1. The actions of the alpha 1-adrenoceptor antagonist tamsulosin have been examined at functional alpha 1-adrenoceptor subtypes and compared with those at the human prostate receptor. 2. At the alpha 1D-adrenoceptors of the rat aorta, tamsulosin acted as a competitive antagonist with a high affinity (pKB = 10.1). 3. At the alpha 1B-adrenoceptor of the rat spleen and rabbit corpus cavernosum penis, tamsulosin again acted as a competitive antagonist but with a significantly lower affinity (pKB = 8.9-9.2). 4. Tamsulosin acted as an unsurmountable antagonist of the alpha 1A-adrenoceptor-mediated responses of the rat and human vas deferens, reducing maximal responses to phenylephrine by 20% and 50%, respectively, at an antagonist concentration of 1 nM. Responses of depolarized (100 mM KCl) rat vas deferens preparations were unaffected by 10 nM tamsulosin but this concentration reduced maximal responses to 5-hydroxytryptamine (5-HT) in this tissue. 5. When longer antagonist incubation periods (> or = 60 min) were used, tamsulosin behaved as a competitive antagonist on the human prostate with a significantly higher affinity (pKB = 10.0) than obtained at the alpha 1B-adrenoceptor. 6. The data demonstrate that tamsulosin is a high affinity antagonist at functional alpha 1-adrenoceptors with a selectivity alpha 1D > or = alpha 1A > alpha 1B. In some tissues the compound exhibits an additional unsurmountable antagonist action, the clinical significance of which is unknown.

Effects of topical treatment with budesonide on parameters for epidermal proliferation, keratinization and inflammation in psoriasis.

Corticosteroids are important in the treatment of inflammatory dermatoses, such as psoriasis. They have anti-inflammatory, anti-proliferative and immunosuppressive effects. In this study, the effect of budesonide on proliferation, inflammatory cells and cytokines in psoriasis was investigated. In order to elucidate the time course of the different effects of corticosteroid treatment in psoriasis, six patients were treated for 3 weeks with budesonide 0.025% ointment (Preferid), and biopsies were studied immunohistochemically, before treatment and after 1 and 3 weeks of treatment. Clinical scores together with staining with antibodies indicating proliferation, keratin 16, keratin 10, T-lymphocytes, monocytes, polymorphonuclear leukocytes, Langerhans cells, interleukin-1alpha (IL-1alpha), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-alpha), and intercellular adhesion molecule-1 (ICAM-1) were performed. 'Psoriasis area' and 'severity index' (PASI) scores were significantly reduced after 1 week and 3 weeks of treatment. Epidermal hyperproliferation (Ki-67 binding) and suprabasal keratin 16 (Ks8.12) expression decreased within 1 week, while keratin 10 (RKSE60) expression did not change. Five out of 6 patients showed cytokine levels (IL-1alpha, IL-6, IL-8, and TNF-alpha; detected immunohistochemically) in the normal range, while 1 patient had highly increased cytokine levels. In this patient, cytokine levels decreased during treatment. In 4 patients, showing high dermal ICAM-1 expression before treatment, a consistent reduction of ICAM-1 on endothelial cells was observed. The inflammatory infiltrate (T-lymphocytes (T11), monocytes/macrophages (WT14), polymorphonuclear leukocytes (PMN, anti-elastase)) was reduced to some extent after 3 weeks. The number of Langerhans cells (OKT6) did not change. These results indicate that the psoriatic lesions, although clinically comparable, show interindividual differences in cytokine expression. Corticosteroid treatment for 1-3 weeks improves clinical scores and hyperproliferation. Cytokine levels are reduced during steroid treatment in the patient who showed high levels before treatment. To suppress the infiltrate entirely, longer steroid treatment is probably necessary. This may explain the relapse seen after short term corticosteroid therapy.

Differential effects of dermatological cream bases with respect to skin surface moisturizing capacity: A study design in volunteers.

The efficacy of creams and ointments on skin surface hydration was assessed in healthy volunteers. The results of two studies showed differential responses to ointments, oil-in-water (o/w) creams and Lipobase (an o/w cream with a high fat content). The present study design is recommended for the easy and reliable preclinical evaluation of topical vehicles.

The hairless mouse as a model for study of local and systemic atrophogenic effects following topical application of corticosteroids.

The hairless mouse has been used as a model to distinguish between local and systemic atrophogenic effects of topical steroids. Hydrocortisone-17-butyrate, betamethasone-17-valerate, budesonide and clobetasol-17-propionate were applied topically daily for 21 days. Skinfold thickness and dermal DNA synthesis of treated and untreated skin were evaluated as parameters of local and systemic atrophogenicity. Further, body weight gain and thymus weight were assessed as markers of systemic activity. With respect to local effects, skin thickness and dermal DNA synthesis both proved to be good parameters. Of the systemic parameters, thymic involution and body weight gain paralleled quite well the skin thinning on the untreated side. The results confirmed the potency differences of the steroids. Furthermore, they emphasize the usefulness of the hairless mouse to assess the relative safety with respect to local and systemic side effects of chronically applied topical corticosteroids.

[Toxicological and pharmacological effects of the use of bovine somatotropin in dairy farming]. / Toxicologische en farmacologische effecten van het gebruik van bovine somatotropine (BST) in de melkveehouderij.

Some possible toxicological and pharmacological consequences of the use of bovine growth hormone (BST) synthesised using recombinant DNA techniques are discussed in the present paper. Three spheres of interest are reviewed. Target species: When BST is used correctly, negative effects on the target species are unlikely to occur. Obscurity may to some extent remain as regards the effect of BST on the immune system. Residues of BST and IGF: There is nothing to suggest that the BST levels in the milk will increase significantly following BST treatment. Slight elevations of the levels of IGF-1 (one of the so-called somatomedins) in the milk following treatment with BST have been reported. However, the concentration of IGF-1 that is reached after the correct use of BST is still lower than that in milk collected during early stages of lactation. As a result of the peptide character of BST and IGF-1, absorption by healthy human individuals is unlikely to occur. The relevance of the problem of BST and/or IGF-1, absorption from milk by some individuals such as young infants is also discussed in this paper. Interaction with the metabolism of drugs: A possible interaction between BST and drugs which are administered to the animal at the same time, as is observed in rats and occasionally also in human subjects could have consequences for the clinical effectiveness, side-effects and drug residues in food products of animal origin. So far, however, an interaction of this type could not be detected in ruminants. At the present time, this phenomenon is being studied in greater detail.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha 1-adrenoceptors: the ability of various agonists and antagonists to discriminate between two distinct [3H]prazosin binding sites.

Recently, it has been demonstrated that two distinct alpha 1-adrenoceptor binding sites showing high and low affinity for WB-4101 (2-(2,6-dimethoxyphenoxy)ethyl-aminomethyl-1,4-benzodioxane) and 5-methyl-urapidil can be distinguished. In the present study we examined the ability of several agonists and antagonists to discriminate between these alpha 1-adrenoceptor binding sites. [3H]Prazosin binding to membranes of rat liver, heart, cerebral cortex and hippocampus was inhibited monophasically by butanserine, I-BE 2254 (2-(3-(4-hydroxy-3-iodophenyl)ethylaminomethyl)tetralone-hydrochloride), prazosin, rauwolscine and verapamil. In contrast, competition curves of adrenaline, oxymetazoline, amidephrine and YM-12617 (5-[2-[[2-(o-ethoxy-phenoxy)ethyl]-amino]propyl]-2- methoxybenzenesulfonamide HCl) were best described by a model of two binding sites. Chloroethylclonidine (CEC), a compound shown to irreversibly eliminate binding sites with low affinity for WB-4101, increased the proportion of high affinity binding sites for oxymetazoline and amidephrine, whereas the binding data for prazosin and adrenaline remained unchanged. These results indicate that amidephrine, oxymetazoline and YM-12617, but not the other drugs tested discriminate between different alpha 1-adrenoceptor recognition sites labelled by [3H]prazosin.

Effect of trenbolone and testosterone on the plasma elimination rates of sulfamethazine, trimethoprim, and antipyrine in female dwarf goats.

Plasma elimination rates of sulfamethazine (100 mg/kg of body weight, IV), trimethoprim (20 mg/kg, IV), and antipyrine (35 mg/kg, IV) were studied in adult female dwarf goats (n = 5) before and after implantation with trenbolone acetate (5 mg/kg). Pretreatment with trenbolone caused a significant decrease in the elimination rate of the drugs tested: for sulfamethazine, 5 times; for antipyrine, 3 times; and for trimethoprim, 2 times. After treatment with testosterone (1 mg/kg, SC, twice weekly for 2.5 weeks), female goats (n = 5) had a similar decrease in the elimination rate of sulfamethazine. Other induced effects included a change in social behavior, a lower voice, and the development of a typical billy goat-like odor. Plasma creatinine concentrations after androgen administration were significantly higher than those before androgen administration; changes were not observed in plasma urea values. Because of the differences observed, we believe that more attention should be paid to the effects of androgenic agents on drug kinetic properties, with particular reference to studies on clinical efficacy, side effects, and drug residues in food products.

Some pharmacokinetic data of aditoprim and trimethoprim in healthy and tick-borne fever infected dwarf goats.

Aditoprim (AP) is a new dihydrofolate reductase inhibitor, which is structurally related to trimethoprim (TMP). The pharmacokinetics of AP (10 mg/kg) and TMP (20 mg/kg) were assessed in healthy dwarf goats. Therapeutic efficacy against rickettsial infections was tested in tick-borne fever (TBF) infected goats. The animals were given TMP (n = 5) or AP (n = 5) by i.v. injection, and subsequently the drugs were administered orally (same groups, similar doses). Finally, both groups were infected with TBF and the i.v. experiment was repeated. Plasma concentration-time curves for both drugs followed first-order two-compartment decay. For TMP, mean t1/2 beta +/- SEM (h) was 0.84 +/- 0.06 (i.v. control) and 0.90 +/- 0.06 (i.v. infected), respectively, whereas for AP values of 8.00 +/- 0.31 (i.v. control) and 10.28 +/- 0.67 (i.v. infected) were obtained (P less than 0.05). Mean Vd beta +/- SEM values (l/kg) were 3.84 +/- 0.27 (i.v. control) and 4.07 +/- 0.85 (i.v. infected) for TMP (NS) and 7.02 +/- 0.63 vs 9.29 +/- 0.21 (P less than 0.05) for AP. After i.v. injection, rumen fluid concentrations of AP were significantly (P less than 0.05) higher and more persistent than those of TMP. For AP, the plasma and rumen fluid concentrations at 3 h were 1.20 +/- 0.06 micrograms/ml and 0.85 +/- 0.17 microgram/ml, respectively. After oral administration of TMP, Cmax in plasma was 0.12 +/- 0.01 microgram/ml and the maximum was reached after 1.2 +/- 0.16 h; systemic bioavailability (F) was 10.3% (relative to AUC i.v.). Oral treatment with AP resulted in a Cmax value of 0.21 +/- 0.02 microgram/ml with Tmax of 22.5 +/- 1.65 h and a F value of 71%. Based on WBC, serum ALP and rectal temperature responses, it was concluded that both TMP and AP were inactive against Ehrlichia phagocytophila.

The effect of testosterone and rutting on the metabolism and pharmacokinetics of sulphadimidine in goats.

After testosterone pretreatment of castrated goats and during the rutting season of adult entire male goats, the oxidative metabolism of sulphadimidine (SDM) was inhibited markedly compared with the castrated control state of these animals. The oxidation of the 5 position (yielding 5-hydroxysulphadimidine) and of the 6-hydroxymethyl group (yielding 6-carboxysulphadimidine) was decreased equally, with that of the methyl group at the pyrimidine side chain itself being 6-hydroxymethylsulphadimidine (CH2OH), whereas the acetylation pathway was unaffected by testosterone. The consequence of altered metabolism by testosterone was a prolongation of SDM presence in the body. Effects on protein binding of the CH2OH metabolite and on the renal clearance of SDM were also investigated.