Surgical procedure for implanting a radiotelemetry transmitter to monitor ECG, heart rate and body temperature in small Carassius auratus and Carassius auratus gibelio under laboratory conditions

Radiotelemetry provides an alternative means of obtaining physiological measurements from conscious and freely moving animals, without introducing stress artefacts. A surgical procedure is described for implanting radiotelemetry transmitters to monitor the electrocardiogram (ECG), heart rate (HR) and body temperature (BT) in small goldfish ( Carassius auratus; 50–100 g) and Prussian carp ( Carassius auratus gibelio; 100 g). This type of transmitter is commonly implanted in freely moving mice. After surgery and a recovery period of 24 h, the ECG, HR and BT were recorded in freely swimming fish within the limitations of the aquarium.

Effect of conditioning on the increase of heart rate and body temperature provoked by handling in the mouse

To assess the effect of procedures on animal welfare, various physiological parameters, such as body weight, hormone levels in plasma and/or urine, heart rate (HR), blood pressure and body temperature (BT), can be used. When measuring physiological parameters with techniques involving restraint of the animals, the results must be interpreted with caution, since restraint itself may have an effect on those parameters. Radio-telemetry, using an implantable transmitter, provides a way to obtain more accurate and reliable physiological measurements from freely moving animals in their own environment. In this study, we have used radio-telemetry to investigate the influence of conditioning on the increase of HR and BT as provoked by handling of mice. It was found that, after a conditioning period of 12 days, the increase of HR due to handling was significantly reduced.

The effect of ozone exposure on the release of eicosanoids in guinea-pig BAL fluid in relation to cellular damage and inflammation

The observed effects after ozone exposure strongly depend on ozone concentration and exposure time. We hypothesized that depending on the O3 exposure protocol, mainly either an oxidant damage or an inflammation will determine the O3 toxicity. We compared two different ozone exposure protocols: an acute exposure (3 ppm 2 h) for studying the oxidant damage and an exposure (1 ppm 12 h) where an inflammatory component is also probably involved. We measured LDH activity and protein and albumin exudation as markers for cellular damage. After the acute exposure an increase in LDH activity was measured and after exposure to 1 ppm ozone for 12 h the exudation of protein and albumin was also enhanced. The histological examinations showed a neutrophilic inflammatory response only after exposure to 1 ppm ozone for 12 h. The acute exposure protocol resulted in an increased release of PGE2, PGD2, PGF2alpha and 6-ketoPGF1alpha whereas exposure to 1 ppm ozone for 12 h led to an additional release of LTB4. No effects were measured on the release of TxB2 and LTC4/D4/E4. These changed amounts of eicosanoids will probably contribute to the ozone-induced lung function changes.

Oxidative degradation of lipids during mashing

Although hardly any polyunsaturated fatty acids (PUFAs) are present in the endproduct, the ingredients used for the production of beer contain a high concentration of PUFAs, such as linolic and linolenic acid. These compounds are readily oxidized, resulting in the formation of lipid-derived products that reduce the taste and quality of beer enormously. During mashing relatively high amounts of PUFAs are exposed to atmospheric oxygen at a relatively high temperature. This makes mashing a critical step in the brewing process with regard to the formation of lipid-derived off-taste products. F1 phytoprostane (PPF1) changes in antioxidant capacity and monohydroxy fatty acids (OH-FAs) were used as markers for the detection of oxidative damage to fatty acids during mashing. The pattern of OH-FA formation indicates that enzymatic oxidation of PUFAs is more important than nonenzymatic oxidation during the mashing process. Nevertheless, substantial nonenzymatic radical formation is evident from the increase of specific OH-FAs and PPF1s. It was found that a low oxygen tension reduces oxidative damage and gives a high antioxidant capacity of the mashing mixture. This indicates that mashing should be done under low oxygen pressure.

[Erosion effect of a newly developed soft drink]

In this article, the erosion effect of a newly developed soft drink available in 3 different flavours is compared with the erosion effect of some common soft drinks. Several basic parameters of the soft drinks were determined: pH, titratable acidity, and the calcium as well as phosphate concentration. Three methods were used to assess in vitro the erosion depth of the soft drinks in enamel specimens. Erosion depth is defined as the mean height of lost enamel. The methods used were atomic absorption spectroscopy for calcium loss, a colorimetric ammonium molybdate method for phosphate loss and non-contact profilometry for enamel volume loss. The newly developed soft drink realized statistically significantly less erosion depth when compared with cola and apple juice and statistically non-significantly less erosion depth when compared with orange soda.

Antioxidant capacity of reaction products limits the applicability of the Trolox Equivalent Antioxidant Capacity (TEAC) assay

The Trolox Equivalent Antioxidant Capacity (TEAC) assay is based on the scavenging of the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical (ABTS(*)) converting it into a colorless product. The degree of decolorization induced by a compound is related to that induced by trolox, giving the TEAC value. The assay is frequently used for constructing structure activity relationships (SARs). HPLC analysis of the reaction mixture, obtained after scavenging of ABTS(*) by the flavonoid chrysin, shows that a product is formed that also reacts with ABTS(*). The product has a higher antioxidant capacity and reacts faster with ABTS(*) than the parent compound, chrysin. In contrast to the reaction product of chrysin, the reaction product of trolox, which is formed during scavenging of ABTS(*), i.e. trolox quinone, does not react with ABTS(*). The experiments show that the TEAC is the antioxidant capacity of the parent compound plus the potential antioxidant capacity of the reaction product(s). This means that the TEAC assay does not necessarily reflect the antioxidant effect of only one structure. This hampers the applicability of the assay for the construction of SARs and for ranking antioxidants.

Interactions between flavonoids and proteins: effect on the total antioxidant capacity

Flavonoids are potent antioxidants. It is also known that flavonoids bind to proteins. The effect of the interaction between tea flavonoids and proteins on the antioxidant capacity was examined. Their separate and combined antioxidant capacities were measured with the Trolox equivalent antioxidant capacity (TEAC) assay. It was observed that the antioxidant capacity of several components of green and black tea with alpha-, beta-, and kappa-casein or albumin is not additive; that is, a part of the total antioxidant capacity is masked by the interaction. This masking depends on both the protein and the flavonoid used. Components in green and black tea, which show the highest masking in combination with beta-casein, are epigallocatechin gallate and gallic acid. The results demonstrate that the matrix influences the efficacy of an antioxidant.

Masking of antioxidant capacity by the interaction of flavonoids with protein

The effect of antioxidants is often executed in complex biological mixtures where various interactions may take place. Therefore, the antioxidant capacity of antioxidants in blood plasma is examined. The assay used is the trolox equivalent antioxidant capacity (TEAC). This method gives the antioxidant capacity of a compound by measuring spectrophotometrically the disappearance of the blue/green stable ABTS [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] radical, caused by scavenging. The results show that the antioxidant capacity of quercetin, rutin, catechin or 7-monohydroxyethylrutoside (monoHER) and blood plasma is not additive. This is partly due to interactions between the antioxidant and plasma proteins. However, the antioxidant capacity of alpha-tocopherol, which also binds to protein, is not affected by the interaction. This means that besides the antioxidant capacity of the compound itself, the environment in which the antioxidant has to execute his function is important.

The use of radiotelemetry in small laboratory animals: recent advances

Radiotelemetry provides an alternative means of obtaining physiological measurements from awake and freely moving laboratory animals, without introducing stress artifacts. For researchers, especially those in the fields of pharmacology and toxicology, the technique may provide a valuable tool for predicting the effectiveness and safety of new compounds in humans. In light of studies described in the literature, it is concluded that there is ample evidence that the use of radiotelemetry for measuring blood pressure, cardiac activity, heart rate, body temperature, and locomotor activity in rodents has been validated sufficiently. Today, this technology is an important tool for the stress-free collection of these physiologic data in small rodents, including mice.

Inhibition of nitric oxide synthase by nasal decongestants

The nasal decongestants oxymetazoline and xylometazoline are frequently used in the topical treatment of rhinitis and sinusitis. As nitric oxide (NO) is thought to play a role in inflammation of the upper respiratory tract, the aim of this study was to examine the in vitro effects of these compounds on the activity and the expression of NO producing enzymes, including the inducible form of NO synthase (iNOS) and the constitutive isoform of NO synthase (cNOS). Experiments concerning the effects of both compounds on enzymatic activity and enzyme induction of iNOS were performed in a lipopolysaccharide (LPS) induced rat alveolar macrophage cell line (NR8383) using the Griess assay and the 3H-citrulline assay respectively. The effects on cNOS were examined in fresh rat synaptosomes using the 3H-citrulline assay. The direct scavenging properties of both compounds were investigated using a amperometric NO sensor. Oxymetazoline and xylometazoline were shown to have a dose dependent inhibitory effect on total iNOS activity indicated by nitrite/nitrate formation in the Griess assay. This effect was found to be due to an inhibition of induction of the enzyme rather than inhibition of the enzyme activity, as was investigated in two separate experiments using the 3H-citrulline assay. Inhibition of cNOS was moderate and in the same order of magnitude as the inhibition of enzymatic iNOS activity. Direct scavenging of NO could not be detected. As constitutive nitric oxide synthase activity is thought to serve beneficial physiological functions, and exaggerated inducible nitric oxide synthase activity may cause exacerbation of the inflammatory process, pharmacological treatment influencing the nitric oxide generating system should focus on inhibition of inducible nitric oxide synthase alone. The specific characteristics of these decongestants in vitro suggests suitability for this application and may indicate an additional beneficial effect in the treatment of upper respiratory tract inflammation.

Stereoselectivity at the beta2-adrenoceptor on macrophages is a major determinant of the anti-inflammatory effects of beta2-agonists

Previous research has shown that beta-adrenoceptor (beta-AR) agonists have potent anti-inflammatory capabilities, e.g. represented by suppression of release of the proinflammatory cytokines. Aim of this research was to determine whether the effects of beta-agonists on LPS-induced TNFalpha and IL-10 release are influenced by their different stereochemistry. In addition, the role of the beta-AR subtypes was studied. The effect of two stereoisomers of the selective beta2-AR agonist TA2005 [(R,R)- and (S,S)-] on the LPS-induced TNFalpha and IL-10 release by U937 macrophages was compared. The (R,R)-stereoisomer was 277 times more potent in inhibiting the TNFalpha release than the (S,S)-form. The (R,R)-stereoisomer also appeared to be more potent in increasing the IL-10 release. In radioligand binding studies the affinity of (R,R)-TA2005 for the beta-adrenoceptor was 755 times higher than the (S,S)-TA2005 stereoisomer. In addition, the elevation of intracellular cAMP in U937 cells appeared to be stereoselective: (R,R)-TA2005 was more potent in elevating intracellular cAMP. The effect of both stereoisomers on the LPS-induced TNFalpha release could almost completely be antagonized by preincubation with the selective beta2-AR-antagonist ICI-118551. Further evidence that the effect of the beta-agonists is mediated via the beta2-adrenoceptor subtype exclusively was acquired by incubation of U937 cells with selective beta1- and beta3-agonists. None of these receptor subtype agonists showed significant suppressive effect on TNFalpha release. This study provides additional proof that the anti-inflammatory effects of beta2-agonists are mediated via the beta2-adrenoceptor and indicates that these effects are highly dependent on the stereoselectivity of the ligand.

Telemetric monitoring of blood pressure in freely moving mice: a preliminary study

This paper describes for the first time the possibility for recording the systolic pressure (SP), diastolic pressure (DP), and the mean arterial pressure (MAP) as well as the heart rate (HR) and locomotor activity (LA) in freely moving mice, using a commercially available telemetry and data acquisition system. The system comprises a new, small radio-telemetry transmitter implanted in the peritoneal cavity, a receiver board placed underneath the home cage, a multiplexer and a computer-based data acquisition system. The signals from the receiver were consolidated by the multiplexer and were stored and analysed by the computer. The telemetered pressure signals (absolute pressure) were corrected automatically for changes in atmospheric pressure measured by an ambient pressure monitor. The effects of implantation on animal behaviour, and, after the animals had recovered, the effects of handling on the SP, DP, MAP and HR were examined. The radio-telemetry system for recording the SP, DP, MAP and HR provides an accurate and reliable method for monitoring the direct effects of handling on SP, DP, MAP and HR. In addition, by using this new blood pressure (BP) transmitter, we maintain that BP measurements in freely moving mice are more efficient, reliable, and less labour-intensive than the measurement techniques described in the literature thus far.

Nitric oxide synthase inhibition by dimaprit and dimaprit analogues

1. The similarity in molecular structure between the histamine H2-agonist dimaprit (3-dimethylamino-propyl-isothiourea) and the endogenous nitric oxide synthase (NOS) substrate L-arginine prompted us to study the effect of dimaprit and some dimaprit analogues on NOS activity. Dimaprit and some of its analogues were tested in an in vitro assay which measures the conversion of [3H]-L-arginine to [3H]-L-citrulline. Dimaprit inhibits rat brain NOS (nNOS) concentration dependently with an IC50 of 49+/-14 microM. 2. Removal of one or both of the methyl groups from the non-isothiourea nitrogen of dimaprit improved nNOS inhibitory properties. Aminopropylisothiourea is the most potent compound (IC50 = 4.1+/-0.9 microM) of the series followed by methylaminopropylisothiourea (IC50 = 7.6 +/- microM). 3. The observed effect of aminopropylisothiourea and methylaminopropyl-isothiourea are probably not due to the compounds themselves but to the corresponding mercaptoalkylguanidines, rearrangement products formed in aqueous solutions. This hypothesis is strengthened by the finding that aminobutylisothiourea is not active since a rearrangement to mercaptobutylguanidine does not occur. 4. Remarkably, nitrosylation of the isothiourea group of dimaprit decreases nNOS inhibitory activity, while nitrosylation of the guanidine analogue of dimaprit increases the inhibition of nNOS activity. 5. The pharmacological profile of dimaprit includes inhibition of nNOS. The nNOS inhibitory activity occurs in the same concentration range as the H2-agonist and H3-agonist activity of this compound.

Capsaicin treatment induces muscarinic hyperreactivity in guinea pig trachea: a warning

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is a widely used tool for the depletion of neuropeptides from sensory C-fibres. Upon capsaicin treatment tachykinins are released, resulting in a variety of responses in the airways. We showed that after capsaicin (0.3 microM; 30 min) treatment of guinea pig tracheal smooth muscle preparations, the maximal contraction of the trachea after methacholine stimulation was strongly increased (capsaicin: 1.147 +/- 0.050 g vs. control: 0.717 +/- 0.047 g). This effect was completely nullified after pretreatment with capsazepine (2-[2-(4-chlorophenyl)ethyl-amino-thiocarbonyl]-7,8-dihydroxy-2,3, 4,5-tetrahydro-1H-2benzazepine; a vanilloid receptor antagonist) and YM38336 (a dual tachykinin NK1 and tachykinin NK2 receptor antagonist). Our results serve as a warning against using capsaicin as a putatively clean pharmacological tool to deplete the neuropeptides from pools on the C-fibres because we showed that capsaicin also strongly influences basal mechanisms in tracheal smooth muscle control.

Oral endotrachael intubation of guineapigs

Oral endotracheal intubation of guineapigs as reported in the literature, is considered to be extremely difficult. Because of this, we constructed special equipment and developed a technique to facilitate the procedure. A special restraint device was designed to position the guineapig. Utilizing a laryngoscope and an operating microscope for visualization then makes intubation easy to perform.

The role of prostanoids in ozone-induced changes in airway responsiveness: receptor activation-specific prostanoid release

We studied the effect of in vivo ozone exposure (3 ppm, 2 h) on methacholine- and histamine-induced guinea pig tracheal smooth muscle contractions in vitro and the role of cyclooxygenase products in this process. After exposure to ozone, methacholine stimulation showed a functional hyperreactivity, whereas after stimulation with histamine a hyporeactivity was observed. These effects could be explained by the release of prostanoids. In a control situation an increase in PGF(2α), PGE(2) and PGD(2) release is observed after stimulation of the histaminergic receptor system. After ozone exposure the release of prostanoids was also enhanced (unstimulated, PGF(2α) and TxB(2); histamine, PGF(2α), PGE(2); methacholine, PGF(2α), TxB(2), 6-kPGF(1α), PGE(2)). This study shows that the prostanoid release is strongly dependent on the receptor system stimulated to induce smooth muscle contraction and the importance of prostanoids in ozone-induced changes in guinea pig tracheal smooth muscle reactivity.

A method for measuring nitric oxide radical scavenging activity. Scavenging properties of sulfur-containing compounds

A new method for the quantification of the nitric oxide (.NO) scavenging activity of compounds in aqueous solutions is described using an amperometric .NO sensor. After correction for the spontaneous degradation of .NO, second-order rate kinetics of the scavenging reaction are observe. The rate constant for hemoglobin found with this method is comparable with that found with an established spectrophotometric method. To demonstrate the capability of the method, several sulfur-containing compounds were tested (GSH, GSSG, S-methyl glutathione, N-acetyl cysteine, lipoic acid and dihydrolipoic acid). Of these compounds, only those that contained a thiol group displayed a considerable .NO scavenging activity.

Changes in neuroreceptor function of tracheal smooth muscle following acute ozone exposure of guinea pigs

We studied the effect of in vivo ozone inhalation (3 ppm, 2 h) on neuroreceptor function in guinea pig tracheal smooth muscle in vitro and the role of the epithelial layer in this process. Changes in smooth muscle tension after stimulation of the muscarinic- and beta-adrenergic receptor were recorded isometrically and stained tracheal tissue sections were histologically evaluated for changes in the epithelial and smooth muscle layer. Ozone exposure resulted in an increase in maximal contraction following stimulation of the muscarinic receptor, whereas pD2 values remained unchanged. After stimulation of the beta-adrenergic receptor no increase in maximal relaxation but only an increase in pD2 value was observed after correction for differences in precontraction level in control- and ozone-exposed situations. Mechanical removal of the epithelial layer resulted in a slight increase of the maximal contraction level after stimulation with methacholine in the control situation, whereas exposure to ozone resulted in a strong decrease of the maximal contraction level under these conditions. Histological stainings showed a slight and focal influx of neutrophilic granulocytes in the epithelial layer, submucosal layer and airway lumen after exposure to ozone. These data support the idea that ozone is able to increase the maximal degree of airway narrowing upon muscarinergic stimulation, i.e. a hyperreactivity response. The results also suggest that functionally altered epithelium plays an important role in the process of ozone-induced hyperreactivity, possibly linked with an early inflammatory response.

Antioxidant levels in the nasal mucosa of patients with chronic sinusitis and healthy controls

BACKGROUND

Imbalances between oxidant formation and antioxidative defense are associated with the pathogenesis of several chronic inflammatory disorders of the respiratory tract. Therefore, a role of oxidative stress in chronic upper airway tract infections can be anticipated.

OBJECTIVE

To determine if patients with chronic sinusitis demonstrate a reduced antioxidative tissue status.

DESIGN

The levels of 3 biologically important antioxidants, reduced glutathione and oxidized glutathione, uric acid, and vitamin E, were determined biochemically in mucosal biopsy specimens from the uncinate process of patients with chronic sinusitis and healthy controls.

SUBJECTS

Inflamed mucosa samples were obtained from 9 patients with chronic sinusitis during functional endoscopic sinus surgery. Normal mucosa samples were collected from 10 healthy controls during surgery for nasal obstruction.

RESULTS

The data (presented as mean +/- SD) show a significant reduction (P < or = .05) of reduced glutathione levels (0.3 +/- 0.1 mumol/g wet weight) and uric acid levels (2.7 +/- 0.4 mumol/g wet weight) in mucosa samples obtained from patients with chronic sinusitis compared with healthy controls (0.6 +/- 0.2 and 3.4 +/- 0.6 mumol/g wet weight, respectively). No difference was found in oxidized glutathione (24 +/- 8 vs 25 +/- 15 nmol/g wet weight) and vitamin E (20.5 +/- 7.9 vs 22.5 +/- 6.9 nmol/g wet weight) levels between both groups.

CONCLUSIONS

Decreased levels of both reduced glutathione and uric acid in patients with chronic sinusitis lead to a diminished antioxidant defense, which may be associated with the pathogenesis of upper respiratory tract disorders. The vitamin E level seems less important. This finding may offer perspectives for pharmacotherapeutic intervention with antioxidants.

Acute exposure to ozone does not influence neuroreceptor density and sensitivity in guinea pig lung

The effects of acute exposure of guinea pigs to 3 ppm of ozone for 2 h on the receptor density and sensitivity of the muscarinergic-, the histaminergic- and the beta-adrenergic receptor systems were studied, in order to provide more insight in the complex mechanisms underlying the well known ozone-induced changes in receptor functionality. The exposure to ozone did not change either the total amount of receptors present in lung tissue, nor the receptor sensitivity of the systems studied. Although no effects were observed, this does not yet fully exclude the receptor system for being a target of ozone exposure. The receptor function can be changed after exposure to ozone, e.g., the coupling with the G-protein can be influenced. Furthermore, the G-protein itself may have been altered or changes can occur at lower levels in the receptor signal transmission route leading to functional changes after stimulation of the receptor with an agonist.

Anti-oxidant actions of oxymethazoline and xylomethazoline

Anti-oxidant actions of oxymethazoline and xylomethazoline were investigated by measuring inhibition of microsomal lipid peroxidation and hydroxyl radical scavenging activity. Oxymethazoline was shown to be a potent inhibitor of lipid peroxidation (IC50 = 4.9 microM at t = 15 min, IC50 = 8.1 microM at t = 30 min), in contrast to xylomethazoline. Both compounds were excellent hydroxyl radical scavengers. Their rate constants (ks = 1.1 x 10(12) M-1 s-1 for oxymethazoline and ks = 4.7 x 10(10) M-1 s-1 for xylomethazoline) exceeded the rate constant of a known powerful scavenger cimetidine (ks = 1.8 x 10(10) M-1 s-1). The difference in inhibiting lipid peroxidation might be explained by the fact that only oxymethazoline has a hydroxy group which can donate a hydrogen atom and terminate the chain reaction of lipid peroxidation. The mechanism of hydroxyl radical scavenging activity is still unclear. Moreover oxymethazoline seems to have a different mode of action in scavenging hydroxyl radicals than xylomethazoline and cimetidine which results in an extremely high rate constant. Because oxidants play a role in tissue damage in inflammation, it was hypothesized that especially oxymethazoline and to a lesser extent xylomethazoline may have an additional beneficial effect, due to their anti-oxidant properties, in the topical treatment of nasal inflammation.

Characterization of the binding of the first selective radiolabelled histamine H3-receptor antagonist, [125I]-iodophenpropit, to rat brain

1. The binding of the first selective radiolabelled histamine H3-receptor antagonist [125I]-iodophenpropit to rat cerebral cortex membranes was characterized. 2. [125I]-iodophenpropit, radiolabelled to a high specific activity of 1900 Ci mmol-1, saturably bound to a single class of sites with a KD of 0.57 +/- 0.16 nM (n = 4) and Bmax of 268 +/- 119 fmol mg-1 protein. 3. Specific binding at a concentration below 1 nM represented 50 to 60% of total binding. 4. Binding of [125I]-iodophenpropit to rat cerebral cortex membranes was readily displaced by histamine H3-agonists and antagonists. In contrast, the inhibitory potencies of selective histamine H1- and H2-receptor ligands were very low. 5. [125I]-iodophenpropit was biphasically displaced by the histamine H3-receptor antagonists, burimamide and dimaprit, which may indicate the existence of histamine H3-receptor subtypes. Other histamine H3-receptor antagonists showed a monophasic displacement. 6. Competition binding curves of H3-agonists were biphasic and showed a rightward shift upon the addition of the nonhydrolysable GTP analogue, guanosine 5'-o-(3-thio) triphosphate (GTP gamma S; 100 microM) which implicates the interaction of histamine H3-receptors with G-proteins. The affinities of the H3-receptor antagonists iodophenpropit, thioperamide and burimamide were not altered by GTP gamma S. 7. Histamine competition binding curves were shifted to the right by different nucleotides (100 microM) with a rank order of potency GTP gamma S > Gpp(NH)p, GTP. 8 In vitro autoradiographic studies revealed a heterogeneous distribution of [125I]-iodophenpropitbinding sites in rat brain, with highest densities observed in specific cerebral cortical areas and layers,the caudate-putamen complex, the olfactory tubercles, the hippocampal formation, the amygdala complex, the hypothalamic area and the mammillary bodies.9 It is concluded that the histamine H3-receptor antagonist, [125I]-iodophenpropit, meets the criteria fo ra suitable radioligand for histamine H3-receptor binding studies in rat brain.

A functional beta-2 adrenoceptor-mediated chronotropic response in isolated guinea pig heart tissue: selectivity of the potent beta-2 adrenoceptor agonist TA 2005

Responses were measured of the highly potent beta-2 adrenoceptor agonist TA 2005, a new bronchodilator, on isolated guinea pig right and left atria and papillary muscle. The main objectives of the study were to investigate the selectivity of the compound and to determine whether guinea pig isolated heart tissues could be used as a model for investigating mechanisms of clinical cardiac side effects. It was found that the inotropic responses in all tissues were mediated by the beta-1 adrenoceptor only. TA 2005 was a partial agonist for the inotropic response compared with I-isoprenaline. For the right atrial chronotropic response, however, TA 2005 exerted a biphasic effect and reached 84% of the I-isoprenaline response. The first phase was mediated by the beta-2 adrenoceptor, whereas the second phase was beta-1 adrenoceptor mediated. Approximately 64% of the TA 2005 chronotropic response was exerted via the beta-2 adrenoceptor. Addition of the beta-2-selective antagonist ICI 188.551 blocked the beta-2 adrenoceptor-mediated response, providing only a monophasic response. Addition of the beta-1-selective antagonist ICI 89.406 resulted in further separation of the phases. The finding that a beta-2-mediated chronotropic response exists on the right atrium of the guinea pig sheds new light on selectivity studies. It is suggested that quantification of beta-1/beta-2 selectivity of beta adrenoceptor agonists be performed not on the basis of measurement of guinea pig right atrial chronotropism but rather on the basis of measurement of guinea pig left atrial inotropism.(ABSTRACT TRUNCATED AT 250 WORDS)

A new radioligand binding assay for cytochrome P450IID1 (CYP2D1) in rat liver microsomes: a tool to predict sparteine/debrisoquine type polymorphism of drugs

[3H]-Mepyramine ([3H]-pyrilamine) has a high affinity for cytochrome P450IID1 (CYP2D1) in rat liver microsomes, the isoenzyme involved in the oxidative metabolism of debrisoquine. Drugs known to interact with this enzyme, as either substrate or inhibitor, displaced [3H]-mepyramine. Compounds specific for other P450 isoenzymes did not displace [3H]-mepyramine. Drugs that are positive in this binding assay can be either substrates or inhibitors of CYP2D1 and warrant further research to investigate possible polymorphism. Substrates could reach toxicological concentrations, and inhibitors can have drug interactions with known CYP2D6 substrates. Although care should be taken in the extrapolation from rat to human, since CYP2D1 and CYP2D6 have clear differences, this rapid, easy-to-perform and inexpensive assay has predictive value for the sparteine/debrisoquine type of polymorphic behavior of compounds and could be used at an early stage in drug development.

Use of telemetry to record electrocardiogram and heart rate in freely moving mice

This paper describes for the first time the possibility to record the electrocardiogram (ECG) and heart rate (HR) with a commercially available telemetry and data acquisition system in freely moving mice. The system comprises a telemetry transmitter implanted in the peritoneal cavity and a receiver, placed underneath the home cage, an A/D converter (MacLab) and a Macintosh LC II 4/80 computer with software (MacLab, Chart/Scope). The raw analog ECG data are digitized within the MacLab and can be converted to HR data additionally. The effects of surgery for implanting the transmitter, handling and anesthesia by either Nembutal or a mixture of Hypnorm, Dormicum, and water, on the changes in ECG and HR were examined. The telemetry system for recording the ECG and HR provides an accurate and reliable method for monitoring the direct effects of handling on HR. By using this telemetry system, we maintain that measurements in freely moving animals are more efficient, reliable, and less labor-intensive than the measurement techniques described in the literature thus far.

Atypical molecular pharmacology of a new long-acting β2-adrenoceptor agonist, TA 2005

The molecular pharmacology of a new putative long-acting bronchodilator TA 2005 (8-hydroxy-5-[(1R)-1-hydroxy-2-[N-[(1R)-2-(p-methoxy-phenyl)- 1-methylethyl]amino]ethyl]carbostyril hydrochloride) has been compared with that of the reference compounds isoprenaline and salbutamol in both methacholine (3 x 10(-6) M) precontracted guinea pig tracheal smooth muscle relaxation and in bovine trapezium muscle binding experiments. TA 2005 appeared very potent compared with isoprenaline and salbutamol (pD2 values of 9.29 vs. 7.65 and 7.10 respectively). For isoprenaline and salbutamol a shallow displacement curve was observed and addition of the non-hydrolysable GTP analogue guanylyl-imidodiphosphate (GppNHp) gave a rightward shift (pKd,high and pKd,low values of 7.3 and 6.1 vs. 7.0 and 5.4 respectively). For TA 2005 a steep displacement curve was found with only one binding state even without GppNHp (pKd,high value of 8.2). The long duration of action of TA 2005 might be explained by tight binding of this compound to the beta 2-adrenoceptor. The extent of tight binding for TA 2005 was extremely large. The molecular basis of the tight agonist binding phenomenon for TA 2005 seems to be of different origin than for isoprenaline. It is hypothesized that a different mechanism of activation of the beta 2-adrenoceptor may be involved for TA 2005.

Glutathione mobilization during cerebral ischemia and reperfusion in the rat

1. Cerebral ischemia applied for 15 min and followed by a 30 min reperfusion did not change the glutathione (GSH) levels and beta-adrenoceptor density (Bmax) in brain cortex. 2. A significant increase in erythrocyte-lysate GSH concentration (vs control) and a significant decrease of Bmax values in erythrocyte membranes (vs control) was found at the same time. 3. Pretreatment with the alpha-adrenoceptor antagonist phentolamine (5 mg/kg i.p.) prevented the erythrocyte GSH increase but not the decrease of Bmax value. Pretreatment with the beta-antagonist propranolol (2 mg/kg i.p.) did not influence the increase in erythrocyte GSH but circumvented the decrease of Bmax.

The effect of ischemia and recirculation, hypoxia and recovery on anti-oxidant factors and beta-adrenoceptor density. Is the damage in the erythrocytes a reflection of brain damage caused by complete cerebral ischemia and by hypoxia?

This investigation was focussed on the gravity of tissue injury caused by complete ischemia (for five min) and hypoxia (for three weeks) in the cerebral cortex (homogenate) and the erythrocyte lysate or the erythrocyte membrane of the rat in order to investigate if the changes that occur in brain tissue are reflected in the erythrocyte. To this end, glutathione (GSH), superoxide dismutase (SOD) and catalase were measured, also alterations in beta-adrenoceptor density under these two conditions were examined. It was found that in ischemia partial parallelism in changes that occur in the central nervous system (cerebral cortex) and the erythrocyte exists. The SOD activity became higher and the beta-adrenoceptor density (measured as specific (-)-[125I] iodocyanopindolol binding) was decreased in both tissues. However after the hypoxic condition we established a decrease in the number of beta-adrenoceptors in the cerebral cortex but an increase in beta-adrenoceptor density in the erythrocyte.