RESUMEN
The distribution of muscarinic receptors in equine airways was investigated using autoradiography. Frozen sections of tissue from six different levels in the bronchial tree, from the trachea to the distal bronchioles, were incubated in vitro with 1.5 nmol/L of the muscarinic receptor antagonist 1-[N-methyl-3H]scopolamine methyl chloride (3H-NMS). In addition, the subtype pattern of muscarinic receptors was investigated in equine tracheal smooth muscle using radioligand binding with methoctramine, tripinamidc, 4-DAMP-methiodide and pirenzipine as competitors against the binding of 1.3 nmol/L 3H-NMS. The autoradiograms showed specific labelling indicating a high density of muscarinic receptors in smooth-muscle tissue in all levels of the airway tree investigated. Besides muscle tissue, subepithelial glands were the only structures specifically labelled. The dominating subtypes in tracheal smooth muscle investigated with radioligand binding studies were found to be M2 and M4, as both methoctramine (pKd = 8.5) and tripinamide (pKd = 8.6 and 6.7 for two different sites) showed high affinity. The density of the M3-muscarinic receptor subtype was low, but this subtype could be detected with statistical significance when methoctramine was used as the competitor against 3H-NMS binding.
Asunto(s)
Bronquios/metabolismo , Caballos/metabolismo , Receptores Muscarínicos/metabolismo , Tráquea/metabolismo , Animales , Autorradiografía/veterinaria , Unión Competitiva , Femenino , Técnicas In Vitro , Cinética , Masculino , Antagonistas Muscarínicos/farmacología , Músculo Liso/metabolismo , N-Metilescopolamina/antagonistas & inhibidores , N-Metilescopolamina/metabolismo , Receptores Muscarínicos/clasificaciónRESUMEN
OBJECTIVE: To determine pharmacokinetics of terbutaline in healthy horses and to relate serum terbutaline concentrations with the drug's pharmacodynamic effects. ANIMALS: 6 healthy horses. PROCEDURE: Horses were given terbutaline i.v. (10 microg/kg of body weight) and, 1 week later, p.o. (100 microg/kg). Responses to drug administration (eg, heart rate and serum lactate concentration) were measured. Serum terbutaline concentration was measured by means of gas chromatography with mass spectrometry. Protein binding was determined in vitro. RESULTS: Following i.v. administration, median maximum serum terbutaline concentration and mean residence time were 9.3 ng/ml and 30 minutes, respectively. Bioavailability following oral administration was < 1%. All horses developed sweating, trembling, excitement, and tachycardia during i.v. infusion. The 2 horses with the highest serum terbutaline concentrations developed severe tachycardia and CNS stimulation; 30 minutes after the i.v. infusion was completed, they were hyperventilating and lethargic. Heart rate and serum lactate concentration increased as serum terbutaline concentration increased. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that terbutaline is rapidly cleared from the bloodstream following i.v. administration to horses, suggesting that continuous i.v. infusion would be needed to maintain therapeutic serum concentrations. Oral administration of terbutaline to horses is not practical because of the low bioavailability.
Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Agonistas Adrenérgicos beta/farmacocinética , Caballos/fisiología , Terbutalina/farmacología , Terbutalina/farmacocinética , Administración Oral , Agonistas Adrenérgicos beta/administración & dosificación , Agonistas Adrenérgicos beta/sangre , Animales , Área Bajo la Curva , Cromatografía de Gases y Espectrometría de Masas/veterinaria , Semivida , Frecuencia Cardíaca/efectos de los fármacos , Infusiones Intravenosas/veterinaria , Ácido Láctico/sangre , Masculino , Unión Proteica/efectos de los fármacos , Terbutalina/administración & dosificación , Terbutalina/sangreRESUMEN
Isoxsuprine is used in veterinary medicine as a vasodilating agent. The drug has been detected in the urine of horses up to 6 weeks after the cessation of administration. In the present study, the distribution pattern of 3H-isoxsuprine was investigated using whole body autoradiography in mice to find a possible site of retention. Melanin was the only place of retention identified. Additional in vitro studies showed an affinity of isoxsuprine to both melanin and keratin. The K(d) values were 0.02 mmol/l and 1 mmol/l, and the B(max) values were 0.2 micromol/mg and 2 micromol/mg, respectively. A low affinity site with approximately the same K(d) and B(max) as keratin was also detected for melanin. 3H-isoxsuprine was found to have affinity to pigmented horse skin after incubation in vitro and microautoradiography. We believe that affinity to melanin and possibly also to keratin can cause retention of the drug in the body and therefore explain the prolonged excretion of low levels of isoxsuprine in the horse.
Asunto(s)
Agonistas Adrenérgicos beta/farmacocinética , Caballos/metabolismo , Isoxsuprina/farmacocinética , Melaninas/metabolismo , Animales , Autorradiografía , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Piel/metabolismo , Recuento Corporal TotalRESUMEN
Beta2-adrenoceptor agonists are used as bronchodilators in both humans and horses. Of these drugs, clenbuterol is the one most frequently used when treating chronic obstructive pulmonary disease in the horse, while salbutamol and terbutaline are used in the treatment of human asthma. Little is known of the properties of the latter two drugs in equine medicine. We have compared salbutamol and terbutaline with clenbuterol in relation to their ability to relax muscle strips from equine tracheal muscle, precontracted with 40 nM carbachol, in tissue chambers. The affinities of these drugs to the beta2-adrenoceptors in homogenates of the same muscle tissue were also examined. These experiments were performed with radioligand binding studies using the very potent beta-adrenoceptor antagonist 125I-cyanopindolol. The three drugs were almost equipotent in relaxing the muscle strips. The EC50-values for salbutamol, terbutaline and clenbuterol were 5.6, 13.8 and 2.1 nM, respectively, and all three drugs relaxed the preparations completely. In the competitive binding study, however, the Kd-value of clenbuterol was much lower (24 nM) than that of salbutamol and terbutaline (1100 nM and 3900 nM, respectively). The amount of receptors bound at the EC50-value of clenbuterol was 8% compared to less than 1% for salbutamol and terbutaline. This indicates a lower intrinsic efficacy of clenbuterol than of the other two drugs. The beta-adrenoceptor density was 45 +/- 14.3 fmol/mg protein (mean +/- SD) and the Kd-value of 125I-cyanopindolol was 11.4 +/- 3.3 pM.
Asunto(s)
Albuterol/farmacología , Broncodilatadores/farmacología , Clenbuterol/farmacología , Caballos/fisiología , Terbutalina/farmacología , Tráquea/efectos de los fármacos , Albuterol/administración & dosificación , Animales , Unión Competitiva , Broncodilatadores/administración & dosificación , Clenbuterol/administración & dosificación , Relación Dosis-Respuesta a Droga , Enfermedades Pulmonares Obstructivas/tratamiento farmacológico , Enfermedades Pulmonares Obstructivas/veterinaria , Relajación Muscular/efectos de los fármacos , Receptores Adrenérgicos beta 2/efectos de los fármacos , Terbutalina/administración & dosificación , Tráquea/fisiologíaRESUMEN
Strips of tracheal smooth muscle from 12 horses were contracted by carbachol in tissue baths under isometric conditions. This contraction (approximately 50% of maximum: EC50) was relaxed completely with adrenoceptor drugs. The only exception was clenbuterol, where the degree of relaxation was approximately 90%. In all horses the EC50-value for isoprenaline (mean 1.6 x 10(-8) M) was less than that for adrenaline (mean 9.6 x 10(-8) M) and noradrenaline (mean 1.8 x 10(-6) M). The potency ratio was 1 < 6 < 110 which indicates that the beta 2-subtype dominates among the beta-adrenoceptors of equine airways. All preparations were also very sensitive to the specific and potent beta 2-receptor agonists clenbuterol (mean 5.7 x 10(-9) M) and procaterol (mean 3.6 x 10(-10) M). No differences in EC50-values due to age, sex and breed were observed in this material. The standard deviation of the mean EC50-values seems to be larger for the specific beta 2-adrenoceptor agonists than for the unspecific. A reason for this could be differences in the pattern of the beta-adrenoceptor population.
Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Relajación Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Animales , Carbacol/antagonistas & inhibidores , Relación Dosis-Respuesta a Droga , Femenino , Caballos , Masculino , Parasimpaticomiméticos/antagonistas & inhibidores , Tráquea/efectos de los fármacosRESUMEN
After intravenous administration of theophylline, microdialysis has been used for studying the non protein bound theophylline concentration in blood and in lung tissue in the rat as well as in two horses. The distribution pattern of 14C-theophylline in the rat was also investigated. When the distribution of theophylline was completed the time course of free drug in the interstitial fluid in lung tissue was in good agreement with the total concentration-time profile in plasma in both species. In the rat the free concentration of theophylline in the lung was slightly lower than the free concentration in the blood from 40 to 300 min. The in vivo protein binding in blood was 48.8 +/- 6.2% in the rats (n = 9) and 8-25% in the horses (n = 2). The whole body autoradiography study in rat showed that the concentration of radioactivity in the lung followed the blood concentration very closely up to 24 h after injection. The effect of theophylline in the lung can be assumed to be related to the plasma concentration of theophylline, since the concentration-time profile in plasma reflects the time course in the lung.
Asunto(s)
Autorradiografía , Caballos/metabolismo , Teofilina/farmacocinética , Animales , Diálisis , Femenino , Inyecciones Intravenosas , Mucosa Intestinal/metabolismo , Riñón/metabolismo , Hígado/metabolismo , Pulmón/metabolismo , Masculino , Sistema Nervioso/metabolismo , Ratas , Ratas Sprague-Dawley , Teofilina/sangre , Distribución TisularRESUMEN
Methods for preparation of labelled ochratoxin A and B are described. The method for preparation of labelled ochratoxin B involves the synthesis of the azide of ochratoxin beta via the mixed anhydride and subsequent conjugation to labelled phenylalanine to yield 14C-ochratoxin B. The labelled ochratoxins were injected into male Wistar rats and after different survival times they were sacrificed and subjected to whole body autoradiography. The distribution pattern of ochratoxin A in the rat did not differ from that earlier registered for mouse. The previously known, high susceptibility of rats (and not mice) to ochratoxin A-induced cancer could thus not be explained by an accumulation of the toxin in specific cells or organs. The distribution patterns of ochratoxin A and B were almost congruent--the only apparent difference being a much longer retention of the labelled ochratoxin A in the blood compared to ochratoxin B, which was much faster excreted. When analyzing tissue extracts for labelled metabolites only the extracts from the rats injected with ochratoxin B were found to contain easily detectable concentrations, while no metabolites of ochratoxin A were seen.
Asunto(s)
Ocratoxinas/síntesis química , Recuento Corporal Total/métodos , Animales , Autorradiografía/métodos , Radioisótopos de Carbono , Cromatografía en Capa Delgada , Ocratoxinas/química , Ocratoxinas/farmacocinética , Especificidad de Órganos/fisiología , Ratas , Ratas EndogámicasRESUMEN
To evaluate the effects of clenbuterol on cardio-respiratory parameters and blood lactate relation to exercise tolerance, experimental horses performed standardized exercise tests on a high-speed treadmill before and after administration of the drug. Clenbuterol was administered in feed to six healthy Standardbreds at a dose rate of 0.8 micrograms/kg b.wt twice daily for 5.5 days. Each horse was tested twice, without and with a respiratory mask, during two consecutive days. One week elapsed between the baseline tests without drug and the tests with clenbuterol treatment (each horse served as its own control). The results show an unchanged heart rate response to exercise 2 h after the last clenbuterol administration. The blood lactate response and the arterial oxygen tension during exercise did not differ before and after drug treatment. The oxygen uptake as well as pulmonary ventilation relative to the work load performed was essentially unaffected. The arterial pH during exercise was significantly increased (P less than 0.05) following clenbuterol treatment. Plasma levels of clenbuterol were maximal 2 h post-administration with values between 0.45 and 0.75 ng/ml. The plasma half-life of elimination was 10.4 h (+/- 2.25 SD). In conclusion, clenbuterol did not cause any major effects on the cardio-respiratory and blood lactate parameters studied in healthy horses performing submaximal exercise tolerance tests.
Asunto(s)
Clenbuterol/farmacología , Frecuencia Cardíaca/efectos de los fármacos , Caballos/fisiología , Esfuerzo Físico/efectos de los fármacos , Respiración/efectos de los fármacos , Administración Oral , Animales , Clenbuterol/administración & dosificación , Clenbuterol/farmacocinética , Prueba de Esfuerzo/veterinaria , Femenino , Semivida , Caballos/sangre , Caballos/metabolismo , Concentración de Iones de Hidrógeno , Lactatos/sangre , Masculino , Oxígeno/sangre , Oxígeno/metabolismo , Volumen de Ventilación Pulmonar/efectos de los fármacosRESUMEN
The distribution patterns of ochratoxin A and its nontoxic dechloro-analogue ochratoxin B were studied in rats using whole-body autoradiography. No prominent difference in distribution patterns was found that could explain why the rat is the animal most susceptible to ochratoxin A-induced renal cancer or why ochratoxin B is less toxic than ochratoxin A.
Asunto(s)
Ocratoxinas/farmacocinética , Ratas/metabolismo , Animales , Autorradiografía , Cromatografía en Capa Delgada , Inyecciones Intravenosas , Tasa de Depuración Metabólica , Ocratoxinas/administración & dosificación , Ratas Endogámicas/metabolismo , Distribución TisularRESUMEN
The distribution of 35-S-labelled cysteine and methionine in the epidermis of the equine hoof following 2 hours of intra-arterial injection was studied by microautoradiography. Material for autoradiography was obtained by biopsy about 1 hour after termination of the intra-arterial injection and also 10 and 40 days later. In the specimens obtained one hour after the injection of labelled cysteine and methionine, the amount of radioactivity in the matrix and in the most proximal part of the laminar layer was very high. There was a clear difference between the distribution of the two labelled amino acids in the keratinizing epidermis of the hoof. Cystine was located mainly in keratinocytes of the keratogenous zone in the matrix and in the nucleated keratinocytes that formed the incompletely keratinized basal part of the primary epidermal laminae and covered the lateral surface of the outer, fully keratinized part of those laminae. Methionine was located mainly in the stratum basale and in the stratum spinosum of the matrix and in the secondary epidermal laminae of the laminar layer. In the specimens obtained 10 days after injection of labelled cysteine a considerable number of keratinocytes, both in the matrix and in the laminar layer, had attained terminal differentiation with residual labelling. Neither in the cysteine specimens obtained after 40 days or in the methionine specimen obtained after 10 days was radioactivity significantly above the basal level observed in the hoof epidermis. The possible importance of the results for research on the pathogenesis of laminitis and on the growth of the hoof is discussed.
Asunto(s)
Cisteína/metabolismo , Epidermis/metabolismo , Pezuñas y Garras/metabolismo , Caballos/metabolismo , Metionina/metabolismo , Animales , Autorradiografía , Femenino , MasculinoRESUMEN
Tritium-alpha-fluoromethyl histidine (3H-alpha-FMH), designed as a kcat-inhibitor of mammalian histidine decarboxylase (EC 4.1.1.22), was administered intravenously in male and pregnant female mice of the NMRI strain and the distribution of tritium in the body recorded by whole-body and microautoradiography. The results showed penetration of radioactivity into most tissues within 5 min. after the injection. After 4 hrs the highest levels of radioactivity were present in the intestinal content and in the kidneys. In the pregnant animal there was also a high labelling of the foetal tissues. When whole-body sections were washed in TCA prior to the autoradiographic exposure to retain only protein-bound radioactivity, a distinct labelling pattern was seen in the kidneys of the pregnant female mice but not in those of the male mice. Microautoradiography of the kidneys showed that the cells involved were located within the proximal convoluted tubuli. In several mouse strains, including the NMRI, the activity of kidney histidine decarboxylase is low in the males but high in females during a transient period of pregnancy. Incorporation of tritium into kidney protein after treatment with 3H-alpha-FMH, was correlated to a loss in histidine decarboxylase activity. The isotopic labelling was confined mainly to a component which cofractionated with histidine decarboxylase in polyacrylamide gel electrophoresis (PAGE) under non-denaturing conditions. Our data indicate that the cells described above represent the location of kidney histidine decarboxylase.
Asunto(s)
Carboxiliasas/metabolismo , Histidina Descarboxilasa/metabolismo , Histidina/análogos & derivados , Riñón/enzimología , Metilhistidinas , Animales , Autorradiografía , Dopa-Decarboxilasa/metabolismo , Femenino , Riñón/anatomía & histología , Cinética , Masculino , Ratones , Peso Molecular , Embarazo , Proteínas/metabolismoRESUMEN
Carbonic anhydrase (CA) isozymes CA I and CA II were isolated from rat erythrocytes, and CA III from rat skeletal muscle. They were purified to homogeneity and labelled with 125I using the Bolton-Hunter method. The tissue distribution of these [125I]CA isozymes was studied in rats with whole-body autoradiography at various times after an intravenous injection. The distribution pattern showed a remarkable organ specificity. CA I and CA III were to a great extent localized to the renal cortex. This is compatible with renal uptake, secondary to glomerular filtration, of these isozymes. This would be expected from the renal handling of proteins with the following characteristics: molecular weight of 29,000; iso-electric points, pI, around 7.2 and 6.5 respectively. However, CA II of similar molecular shape and size, with a pI of 6.8, remained in the blood and was preferentially localized to the liver. Further studies are needed to clarify why such similar proteins are targeted to different organs.
Asunto(s)
Anhidrasas Carbónicas/farmacocinética , Animales , Autorradiografía , Radioisótopos de Yodo/farmacocinética , Ratas , Ratas Endogámicas , Distribución TisularRESUMEN
The pharmacokinetics of theophylline at rest and the effects on cardio-respiratory and blood lactate responses to exercise were investigated after repeated oral administrations in six healthy Standardbred horses. A dose of 5 mg/kg body weight was administered every 12 h. The binding of theophylline to plasma protein was also determined. There was good agreement between predicted and observed plasma concentrations of theophylline at steady state. The mean half-life of elimination was shown to be 17.0 +/- 2.5 h, the mean half life of absorption was 1.6 +/- 1.8 h, the apparent volume of distribution was 852 +/- 99.0 ml/kg and total plasma clearance 0.61 +/- 0.08 ml/kg/min. Theophylline showed very low plasma protein binding (12%). The heart rate and blood lactate levels, during and after exercise, were significantly increased during theophylline-treatment. There was an increase of the arterial oxygen tension after exercise and the arterial carbon dioxide values before and after exercise were significantly lower than the premedication values. No severe adverse effects of the drug were noted. The recommended oral dose is therefore 5 mg/kg every 12 h but due to inter-individual variation, an adjustment of the dose may be necessary. The changes in the studied exercise parameters indicate that the performance capacity may be impaired by theophylline in the healthy horse.
Asunto(s)
Frecuencia Cardíaca/efectos de los fármacos , Caballos/fisiología , Esfuerzo Físico , Respiración/efectos de los fármacos , Teofilina/farmacocinética , Administración Oral , Animales , Proteínas Sanguíneas/metabolismo , Dióxido de Carbono/sangre , Femenino , Masculino , Tasa de Depuración Metabólica , Oxígeno/sangre , Unión Proteica , Teofilina/administración & dosificación , Teofilina/farmacologíaRESUMEN
The tissue distribution of 14C-labeled ochratoxin A was studied in mouse using whole-body autoradiography. The distribution was followed for 18 days after one single intravenous injection of 5 microCi/animal, corresponding to 160-230 ng toxin/g body weight. Very long persistence of 14C-ochratoxin A in the circulation was noticed and the toxin was detected in the blood even after 18 days when the experiment was finished. The radioactivity in the kidney was unequally distributed with a slightly higher concentration in the inner cortical and medullary parts. This was seen from 24 hrs and on after injection. Very high concentrations of radioactivity were found in the bile of treated animals. The radioactivity extracted from several sections was chemically characterized with thin-layer chromatography and was found to represent 14C-ochratoxin A.
Asunto(s)
Ocratoxinas/farmacocinética , Animales , Autorradiografía , Médula Ósea/metabolismo , Radioisótopos de Carbono , Sistema Cardiovascular/metabolismo , Sistema Digestivo/metabolismo , Inyecciones Intravenosas , Ratones , Ocratoxinas/administración & dosificación , Piel/metabolismo , Distribución Tisular , Sistema Urogenital/metabolismo , Recuento Corporal TotalRESUMEN
Tissue distribution of the nephrotoxic mycotoxin ochratoxin A was characterized in laying Japanese quail by whole body autoradiography and scintillation counting using 14C-labelled toxin. Periodically for 8 days after one intravenous injection of 14 microCi/bird, corresponding to 70 ng/g body weight, birds were killed, frozen, and sagittal sections of the whole body were placed on X-ray film. In general, the ochratoxin disappeared from the avian body rapidly. Specific retention of radioactivity was seen as a ring-like distribution in yolks and growing follicles. After sectioning, organs and intestinal contents were removed from carcasses in a frozen condition, homogenized, extracted, chromatographed, and the radioactivity in fractions was measured by scintillation spectroscopy. High concentrations of ochratoxin A were found in gastric intestinal contents, probably originating from toxin excreted in the bile.
Asunto(s)
Coturnix/metabolismo , Ocratoxinas/farmacocinética , Codorniz/metabolismo , Animales , Autorradiografía , Femenino , Ocratoxinas/análisis , Distribución Tisular , Recuento Corporal TotalRESUMEN
Bovine copper/zinc superoxide dismutase (SOD) was labelled with 125I using the chloramine-T method. The tissue distribution of 125I-SOD (dose of SOD 5 mg/kg) was studied with whole-body and microautoradiography at various times after an intravenous injection. The distribution of 125I-SOD showed a remarkable organ specificity in that the localization of the enzyme to the kidneys and the urinary tract completely dominated the autoradiograms. The time pattern of localization of 125I-SOD also gives a clear picture of the renal handling of the enzyme in that, as a consequence of the renal elimination, the enzyme rapidly disappears from the circulation with an elimination half time of about 6 min. Up to 20 min. after the injection, there were high concentrations of 125I-SOD in the renal pelvis, ureter and urinary bladder showing that in addition to renal uptake there was an initial substantial urinary excretion of the enzyme. From the microautoradiography it is clear that the grains were exclusively localized over proximal tubular cells and tended to be concentrated at the luminal rather than the peritubular side of tubule. This would be compatible with renal uptake secondary to glomerular filtration of 125I-SOD, which is what one would expect from the renal handling of a protein with a molecular weight around 31,000 and an isoelectric point around pH 5.4. Pretreatment with a large dose of SOD (88 mg/kg) tended to competitively decrease the renal uptake of labelled SOD after 5 min. and apparently further increase its renal excretion. However, a noticeable renal uptake of 125I-SOD was still apparent.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Superóxido Dismutasa/farmacocinética , Animales , Autorradiografía , Bovinos , Femenino , Radioisótopos de Yodo , Ratas , Ratas Endogámicas , Distribución Tisular , Sistema Urinario/metabolismoRESUMEN
Staphylococcal alpha-toxin and a toxin fragment were labeled with N-succinimidyl[2,3-3H]propionate. The labeled compounds retained greater than 95% biological activity. The distribution of labeled staphylococcal alpha-toxin and alpha-toxin fragment after intravenous administration to BALB/c mice was studied with whole-body and microautoradiography. The animals were divided into three groups that received (i) labeled alpha-toxin only, labeled alpha-toxin after prior injection of unlabeled fragment, or labeled fragment only. After 5 min, the distribution patterns were similar in groups 1 and 2, with the highest amounts of radioactivity found in the blood vessels, liver, spleen, lungs, and kidneys, whereas the labeled fragment alone showed no initial accumulation in the lungs. The kidneys continued to show a high concentration of radioactivity, whereas the levels at 60 min had decreased in the other organs. The toxin showed continued stable binding to the proximal tubuli, whereas the toxin fragment seemed to dissociate and was found only in small amounts in the glomeruli. No radioactivity was found in the central nervous system.
Asunto(s)
Toxinas Bacterianas/metabolismo , Proteínas Hemolisinas , Animales , Autorradiografía , Sistema Nervioso Central/metabolismo , Femenino , Riñón/metabolismo , Ratones , Fragmentos de Péptidos/metabolismo , Staphylococcus aureus , Factores de Tiempo , Distribución TisularRESUMEN
Whole-body autoradiography of mice and rats after i.v. administration of 2,3,7,8-[14C]tetrachlorodibenzo-p-dioxin ([14C]TCDD) showed a selective localization of radioactivity in the liver and nasal olfactory mucosa. In microautoradiograms of solvent extracted sections of the skulls of mice given injections of [3H]TCDD, no radioactivity was observed in the olfactory mucosa, suggesting that TCDD is not covalently bound in this tissue. The amount of specific [3H]TCDD binding sites in cytosol from the ethmoturbinates of rats (33 fmol/mg cytosolic protein) was comparable to that of the liver cytosol as estimated by electrophoresis in polyacrylamide concentration gradient gel, and therefore probably too low to explain the retention of radioactivity in the olfactory mucosa. The specific TCDD binding species in the mucosa of the ethmoturbinates exhibited a similar binding affinity for [3H]TCDD, ligand specificity, and molecular weight as the TCDD receptor from rat liver. The 7-ethoxyresorufin O-deethylase activity of the mucosa of the ethmoturbinates was induced less than twice by administration of the TCDD receptor ligand beta-naphthoflavone (5,6-benzoflavone) 40 h before killing. By administration of beta-naphthoflavone (5,6-benzoflavone) 16 h before killing, mRNA coding for cytochrome P-450d but not for cytochrome P-450c was induced to detectable levels in the mucosa of the ethmoturbinal tissue of the rat. The basal activity of 7-ethoxyresorufin O-deethylation of the mucosa of the ethmoturbinates of the rat was comparable to the corresponding activity of the liver. This basal metabolic activity of the ethmoturbinal tissue was only marginally inhibited by antibodies raised against beta-naphthoflavone (5,6-benzoflavone) induced hepatic cytochrome P-450s. Thus, enzymes other than cytochrome P-450c may possibly account for a part of the basal 7-ethoxyresorufin O-deethylase activity in the rodent olfactory mucosa.
Asunto(s)
Dioxinas/metabolismo , Mucosa Olfatoria/metabolismo , Dibenzodioxinas Policloradas/metabolismo , Receptores de Droga/metabolismo , Animales , Benzoflavonas/farmacología , Citocromo P-450 CYP1A1 , Sistema Enzimático del Citocromo P-450/inmunología , Sistema Enzimático del Citocromo P-450/metabolismo , Citosol/metabolismo , Inducción Enzimática/efectos de los fármacos , Masculino , Metilcolantreno/farmacología , Ratones , Ratones Endogámicos , Microsomas Hepáticos/enzimología , Mucosa Olfatoria/enzimología , Oxidorreductasas/inmunología , Oxidorreductasas/metabolismo , Unión Proteica , ARN Mensajero/análisis , Ratas , Ratas Endogámicas , Receptores de Hidrocarburo de Aril , Distribución Tisular , beta-naftoflavonaRESUMEN
The content of hyaluronan (HA), a common connective tissue component, was determined in well defined areas of the rat middle ear. The HA concentration in the pars flaccida of the tympanic membrane was considerably greater than in the pars tensa and areas on the medial wall of the middle ear cavity. The fate of exogenous HA introduced into the middle ear was also studied in rats. Tritium-labelled HA disappeared through the Eustachian tube (ET) and was followed by analysis of the nasopharyngeal secretion. The radioactivity in the secretion reached a peak at 3 h and decreased to almost zero within 12 h, indicating that most of the HA was removed. By autoradiography and direct analysis of the HA concentration and molecular weight distribution the fate of HA after obstruction of the ET was followed. Radioactive HA was confined to the middle ear and no uptake into surrounding tissues could be traced by autoradiography 4 days after application. The amount of HA that could be recovered from the middle ear was constant for up to 6 days. Analysis of the molecular weight distribution of the deposited HA indicated only slow degradation during these 6 days.
Asunto(s)
Oído Medio/metabolismo , Ácido Hialurónico/metabolismo , Animales , Trompa Auditiva/metabolismo , Ácido Hialurónico/farmacocinética , Masculino , Tasa de Depuración Metabólica , Ratas , Ratas Endogámicas , Distribución TisularRESUMEN
The tissue distribution and pharmacokinetics of 3H-budesonide were studied in the mouse after intravenous administration. The drug was rapidly (t1/2 alpha = 0.062 hrs) and extensively distributed into tissues and organs (V beta = 20.3 l/kg and Vss = 9.4 l/kg). The short elimination half-life (t1/2 beta = 1.55 hrs) and high blood clearance (Cl = 9.04 l/hr/kg) demonstrated a rapid elimination of budesonide from the body. Whole-body autoradiography showed very high amounts of radioactivity in the excretory organs liver and kidney. Also in the lung and lymphatic tissues high amounts of radioactivity were noted. The adrenal cortex but not the medulla was heavily labelled. Radioactivity passed the blood-placenta barrier and to some extent the blood-brain barrier. The identity of the radioactivity in some organs was analysed by liquid chromatography. At all times after dosing (up to 4 hours), the dominating part of the lung, spleen and brain radioactivity was attributable to unchanged budesonide. After 60 min., the dominating part of the kidney radioactivity was identified as polar metabolites of budesonide. The liver radioactivity was at all observation times found to consist mainly of polar metabolites, reflecting the efficient liver biotransformation of budesonide.