RESUMO
INTRODUCTION: Instability of QT duration is a marker to predict Torsade de Pointes (TdP) associated with both congenital and drug-induced long QT syndrome. We describe a new method for the quantification of instability of repolarization. METHODS: Female, adult beagle dogs anesthetized with a potent morphinomimetic were treated with either solvent (n=7) or dofetilide (n=7). Poincaré plots with QT(n) versus QT(n+1) were constructed to visualize the beat-to-beat variation in QT intervals from the lead II ECG. Short-term instability (STI), long-term instability (LTI) and total instability (TI) were quantified by calculating the distances of 30 consecutive data-points from the x and y-coordinate to the "centre of gravity" of the data cluster. Dofetilide at 0.0025 to 0.04 mg/kg i.v. (plasma concentrations of 4+/-0.6 to 41+/-2.7 ng/ml), dose-dependently prolonged QT and QTcV (at 0.04 mg/kg i.v.: QT: 280+/-ms versus 236+/-5 ms with solvent; p<0.05 and QTcV: 290+/-9 ms versus 252+/-4 ms with solvent; p<0.05). Concomitantly, the compound induced an increase in the instability parameters in a similar dose-dependent manner (at 0.04 mg/kg i.v.: TI: 6.8+/-0.9 ms versus 1.7+/-0.3 ms; p<0.05, LTI: 3.6+/-0.5 ms versus 1.0+/-0.2 ms; p<0.05 and STI: 4.2+/-0.6 ms versus 1.0+/-0.2 ms; p<0.05). The increases induced by dofetilide were associated with a high incidence of early afterdepolarizations (EADs) in the endocardial monophasic action potential (in 6 out of the 7 compound-treated animals versus 0 out of the 7 solvent animals; p<0.05). CONCLUSION: Quantification of beat-to-beat QT instability by our method clearly detects changes in short-term, long-term and total instability induced by dofetilide, already at pre-arrhythmic doses. Dofetilide administration to anesthetized dogs prolongs ventricular repolarization, concomitantly increases beat-to-beat QT instability and induces early after depolarizations (EADs). As such, the use of these parameters in this in vivo model shows clear potential for risk identification in cardiovascular safety assessment.
Assuntos
Avaliação Pré-Clínica de Medicamentos/métodos , Síndrome do QT Longo/fisiopatologia , Modelos Cardiovasculares , Torsades de Pointes/fisiopatologia , Anestesia , Animais , Fármacos Cardiovasculares/efeitos adversos , Fármacos Cardiovasculares/classificação , Cães , Relação Dose-Resposta a Droga , Feminino , Injeções Intravenosas , Síndrome do QT Longo/induzido quimicamente , Contração Miocárdica , Fenetilaminas/efeitos adversos , Bloqueadores dos Canais de Potássio/efeitos adversos , Sulfonamidas/efeitos adversos , Torsades de Pointes/induzido quimicamenteAssuntos
Ácidos Nucleicos/genética , Receptores Citoplasmáticos e Nucleares/genética , Receptores de Esteroides/genética , Alelos , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes , Genótipo , Humanos , Polimorfismo Genético/genética , Receptor de Pregnano X , Reação em Cadeia da Polimerase Via Transcriptase Reversa , TemperaturaRESUMO
Four neonates with a positive phenylalanine screening test (Phe concentrations between 258 and 1250 micromol/L) were investigated further to differentiate between phenylalanine hydroxylase (PAH) deficiency and variant hyperphenylalaninaemia (HPA) forms. In patients 1 and 2 a tetrahydrobiopterin (BH4) load caused a significant decrease of the plasma Phe levels. A combined phenylalanine/BH4 loading test was performed in patients 2, 3 and 4. In the latter two patients, plasma Phe concentrations completely normalized within 8 h after the BH4 load (20 mg/kg). Basal urinary pterins were normal in all four patients. The activity of dihydropteridine reductase (DHPR) was normal in patients 1, 2 and 3 and 50% of control values in patient 4 (not in the range of DHPR-deficient patients). In patient 3 a subsequent phenylalanine loading test with concomitant analysis of plasma biopterins revealed a normal increase of biopterin, excluding a BH4 biosynthesis defect. Pterins and neurotransmitter metabolites in CSF of patients 1, 3 and 4 were normal. DNA mutations detected in the PAH gene of patients 1-4 were A313T, and L367fsinsC; V190A and R243X; A300S and A403V; R241C and A403V. The results are suggestive for mutant PAH enzymes with decreased affinity for the cofactor BH4.
Assuntos
Biopterinas/análogos & derivados , Biopterinas/uso terapêutico , Fenilalanina Hidroxilase/deficiência , Biopterinas/sangue , Análise Mutacional de DNA , Diagnóstico Diferencial , Di-Hidropteridina Redutase/metabolismo , Feminino , Humanos , Recém-Nascido , Cinética , Mutação , Países Baixos , Fenilalanina/sangue , Fenilalanina Hidroxilase/genética , Polimorfismo Conformacional de Fita Simples , Pterinas/líquido cefalorraquidiano , Pterinas/urinaRESUMO
We report on a patient presenting with mental retardation and obesity and a proximal duplication of chromosome 15. The patient shared some clinical signs with Prader-Willi syndrome. With a region-specific paint, generated by microdissection, a duplication in region 15q11.2-q13 was shown to be present. Subsequently, FISH with probes localized to chromosome region 15q11.2-q12 and microsatellite analysis was used to characterize this chromosome aberration further and an insertion duplication within the region frequently deleted in Prader-Willi and Angelman syndrome was demonstrated.
Assuntos
Cromossomos Humanos Par 15/genética , Duplicação Gênica , Hibridização in Situ Fluorescente/métodos , Síndrome de Prader-Willi/genética , Criança , Aberrações Cromossômicas/genética , Transtornos Cromossômicos , Metilação de DNA , Sondas de DNA/genética , Eletroforese em Gel de Ágar , Deleção de Genes , Marcadores Genéticos , Humanos , Cariotipagem , Masculino , Repetições de Microssatélites/genética , Reação em Cadeia da PolimeraseRESUMO
We report on a patient with a de novo translocation between the long arms of chromosomes 14 and 18. The translocation was studied using microdissection in combination with fluorescence in situ hybridization (micro-FISH). Five copies of the chromosomes involved in the translocation were isolated by microdissection and amplified by means of degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR). Reverse chromosome painting with the biotin-labeled PCR product showed that part of the q-arm of chromosome 18 had no signal. The deletion was characterized further by FISH with band-specific probes and it was concluded that the rearrangement was unbalanced: 46,XY,t(14;18)(14pter-->14q22::18q21.1-->18qter) (18pter-->18q12.2::14q22-->14qter). The patient, who presented with psychomotor retardation, mild obesity, pes equinovarus, strabismus, and facial anomalies, is compared with previously reported patients with an interstitial deletion of band 18q12.
Assuntos
Cromossomos Humanos Par 14/genética , Cromossomos Humanos Par 18/genética , Translocação Genética/genética , Pré-Escolar , Sondas de DNA , Deleção de Genes , Humanos , Hibridização in Situ Fluorescente , Deficiência Intelectual/genética , Cariotipagem , MasculinoRESUMO
We report a rare case of paternally transmitted congenital myotonic dystrophy (DM). The proband is a 23 year old, mentally retarded male who suffers severe muscular weakness. He presented with respiratory and feeding difficulties at birth. His two sibs suffer from childhood onset DM. Their late father had the adult type of DM, with onset around 30 years. Only six other cases of paternal transmission of congenital DM have been reported recently. We review the sex related effects on transmission of congenital DM. Decreased fertility of males with adult onset DM and contraction of the repeat upon male transmission contribute to the almost absent occurrence of paternal transmission of congenital DM. Also the fathers of the reported congenitally affected children showed, on average, shorter CTG repeat lengths and hence less severe clinical symptoms than the mothers of children with congenital DM. We conclude that paternal transmission of congenital DM is rare and preferentially occurs with onset of DM past 30 years in the father.
Assuntos
Distrofia Miotônica/genética , Adulto , DNA/análise , Feminino , Humanos , Masculino , Debilidade Muscular/congênito , Debilidade Muscular/genética , Distrofia Miotônica/congênito , Linhagem , Repetições de TrinucleotídeosRESUMO
Microdissection and fluorescence in situ hybridisation (FISH) were used to elucidate the nature of a complex chromosome translocation, after GTG banding failed in the complete characterisation of the structural rearrangement between chromosomes 6 and 12. These chromosomes were painted with chromosome specific paints and one of the chromosome regions involved in the translocation was isolated by microdissection. Ten copies of the microdissected region were collected with microneedles from GTG banded metaphases, transferred to a collecting drop, and amplified by means of DOP-PCR. The PCR product was labelled with biotin-14-dATP and used as a FISH probe for hybridisation to normal metaphase chromosomes and metaphase chromosomes of the patients (microFISH). FISH with this chromosome region specific painting probe and with chromosome band specific probes enabled the characterisation of a complex chromosome rearrangement with five breakpoints in two chromosomes. This resulted in the following karyotype: 46,XY,t(6;12)(6pter--> 6q12::12q24.1-->12qter;12qter-->12q13.3:: 6q16.2-->6q26::12q13.3-->12q24.1::6q12--> 6q16.2::6q26-->6qter).
Assuntos
Quebra Cromossômica/genética , Adolescente , Bandeamento Cromossômico , Cromossomos Humanos Par 12 , Cromossomos Humanos Par 6 , Citogenética , Sondas de DNA , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Metáfase/genética , Reação em Cadeia da PolimeraseRESUMO
Micro-FISH was used to elucidate the chromosomal origin of marker chromosomes in three patients. Ten copies of marker chromosomes were collected with microneedles from GTG banded metaphases, transferred to a collecting drop and amplified by means of DOP-PCR. The PCR products were labeled with biotin-14-dATP and used as FISH probes for hybridization to normal metaphase chromosomes and to metaphase chromosomes of the patients (reverse painting). With the generation of chromosome region-specific painting probes by PCR amplification of microdissected DNA and subsequent FISH it was possible to identify the marker chromosomes in all patients. One marker appeared to be derived from the centromere region of the X-chromosome and the proximal third of the long arm, one from the centromere region of chromosome 17 and one marker chromosome was identified as an isochromosome 18p.
Assuntos
Aberrações Cromossômicas , Transtornos Cromossômicos , Hibridização in Situ Fluorescente/métodos , Reação em Cadeia da Polimerase/métodos , Adulto , Criança , Pré-Escolar , Feminino , HumanosRESUMO
Microdissection combined with fluorescence in situ hybridization (micro-FISH) was used to visualize deletions in rearranged human chromosomes and in a de novo translocation. In each experiment five copies of a structurally aberrant chromosome or of the two chromosomes involved in the de novo translocation were isolated by microdissection and amplified using DOP-PCR. The PCR products were then used as probes for FISH to metaphase chromosomes of three patients. After reverse chromosome painting, the structurally aberrant chromosomes were completely painted, and the region deleted in the aberrant chromosomes was visible in the normal chromosomes. The smallest deletion that could be demonstrated this way was a microdeletion of approximately 6 x 10(6) bp, which is frequently reported in Angelman and Prader-Willi syndromes.
Assuntos
Deleção Cromossômica , Hibridização in Situ Fluorescente/métodos , Translocação Genética , Criança , Pré-Escolar , Bandeamento Cromossômico , Cromossomos Humanos Par 14 , Cromossomos Humanos Par 15 , Cromossomos Humanos Par 18 , Cromossomos Humanos Par 3 , Feminino , Corantes Fluorescentes , Humanos , Indóis , Recém-Nascido , Masculino , Reação em Cadeia da PolimeraseRESUMO
We report on 2 girls with mosaic tetrasomy 8p. Patient 1 showed the extra iso 8p chromosome in 20% of cultured lymphocytes and 18% of cultured fibroblasts [46,XX/47,XX,+i(8p)]. She presented with growth retardation, mild facial alterations, and motor developmental delay. Patient 2 presented with developmental delay, hypotonia, and slight facial alterations; she had the extra iso 8p chromosome in 94% of cultured peripheral lymphocytes. The patients are compared to the 6 previously reported cases. In our experience, the presently reported patients clinically resemble children with inv dup(8)(p21-p22) and patients with mosaic trisomy 8.
Assuntos
Anormalidades Múltiplas/genética , Aneuploidia , Cromossomos Humanos Par 8 , Deficiências do Desenvolvimento/genética , Mosaicismo , Bandeamento Cromossômico , Inversão Cromossômica , Face/anormalidades , Feminino , Humanos , Lactente , Cariotipagem , Hipotonia Muscular/genéticaRESUMO
Fluorescent in situ hybridization with probes specific for a chromosomal subregion and chromosome-specific libraries (chromosome painting) are important new methods for assessing chromosome rearrangements. In this paper we present four patients with additional chromosomal material on chromosome 8p who have been studied using G-banding techniques, chromosome painting and FISH with cosmid probes specific for the region 8p23.1-->8pter. In all cases we found a partial inversion duplication of 8p along with a deletion of the region 8p23.1-->8pter.
Assuntos
Inversão Cromossômica , Cromossomos Humanos Par 8 , Monossomia , Trissomia , Adulto , Pré-Escolar , Bandeamento Cromossômico , Sondas de DNA , Feminino , Humanos , Hibridização in Situ Fluorescente , Lactente , Cariotipagem , MasculinoRESUMO
Intra-aortic infusion of collagen (100 micrograms/kg in 1 min) elicited an extensive platelet activation and transient but marked reductions of blood flow and increases of peripheral vascular resistance, both responses being more pronounced in collaterals than in normal arterial beds in feline hind legs. Blockade of 5-hydroxytryptamine (5-HT) subtype 2 (5-HT2) receptors for 5-HT (ketanserin or ritanserin, 0.63 mg/kg iv, -10 min) or amine depletion (reserpine, 0.1 mg/kg im, -10 days, + parachlorophenylalanine 100 mg/kg sc daily for 3 days), but not cyclooxygenase inhibition (indomethacin, 5 mg/kg iv) or thromboxane (Tx) A2/prostaglandin endoperoxide receptor antagonism (sulotroban, 2.5 mg/kg iv), largely prevented the collagen-induced perfusion defect without interfering substantially with the platelet activation process. TxA2 synthase inhibition, alone (dazoxiben, 5 mg/kg iv) or combined with TxA2-prostaglandin endoperoxide receptor antagonism (ridogrel, 2.5 mg/kg iv), partially reduced the collagen-induced perfusion defect and limited to a similar extent the initial platelet aggregation and release of 5-hydroxyindoles and TxB2 while increasing plasma levels of prostacyclin. These results suggest that platelet-derived 5-HT dominates over TxA2 in reducing blood flow in collateral-dependent tissue of the cat hindlimb.
Assuntos
Circulação Colateral/efeitos dos fármacos , Ativação Plaquetária/fisiologia , Serotonina/farmacologia , Tromboxano A2/farmacologia , Animais , Plaquetas/efeitos dos fármacos , Gatos , Colágeno/farmacologia , Feminino , Hemodinâmica/efeitos dos fármacos , Membro Posterior/irrigação sanguínea , MasculinoRESUMO
1. The pathways contributing to the platelet adhesion/aggregation reaction elicited by collagen microfibrils, administered to cats in vivo, were analysed. 2. The intra-aortic infusion of collagen (100 micrograms kg-1 in 1 min) caused an extensive activation of platelets, as evidenced by the time-dependent drop of free platelet numbers in whole blood, and the increases of 5-hydroxyindoles (5-HI), 5-hydroxytryptamine (5-HT) and thromboxane B2 (TXB2) levels in plasma, prepared from effluent venous blood sampled from the inferior caval vein. 3. 5-HT2 receptor blockade with ketanserin (0.63 mg kg-1 i.v., 10 min) and cyclo-oxygenase inhibition with aspirin (10 mg kg-1 i.v., 10 min) slightly attenuated the peak reduction of free platelets in whole blood in response to collagen without affecting changes in plasma 5-HI. Aspirin, but not ketanserin, reduced the collagen-induced changes in plasma TXB2, prostaglandin E2 (PGE2) and 6K-PGF1 alpha. 4. Dual TXA2 synthetase inhibition/TXA2-prostaglandin endoperoxide receptor antagonism with ridogrel (5 mg kg-1 i.v., 10 min) halved the drop in free platelets, reduced the release of platelet 5-HI, inhibited the increase in plasma TXB2 and elevated that of 6K-PGF1 alpha and PGE2 in response to collagen. 5. Combined treatment with ketanserin and aspirin reduced the collagen-induced drop of free platelets and the release of platelet 5-HI to a similar extent as ridogrel alone; plasma prostanoids were affected as with aspirin alone. 6. Combined administration of ketanserin and ridogrel virtually eliminated the collagen-induced platelet adhesion/aggregation response and release of 5-HI; prostanoids were affected as with ridogrel alone. 6. Combined administration of ketanserin and ridogrel virtually eliminated the collagen-induced platelet adhesion/aggregation response and release of 5-HI; prostanoids were affected as with ridogrel alone. 7. The results indicate that the interplay between 5-HT and arachidonic acid metabolites is causally involved in the platelet reaction to activation induced by collagen in cats in vivo.
Assuntos
Ácidos Araquidônicos/fisiologia , Colágeno/farmacologia , Ativação Plaquetária/efeitos dos fármacos , Serotonina/fisiologia , Animais , Aorta Torácica/efeitos dos fármacos , Ácido Araquidônico , Ácidos Araquidônicos/metabolismo , Aspirina/farmacologia , Gatos , Inibidores de Ciclo-Oxigenase , Feminino , Ketanserina/farmacologia , Masculino , Músculo Liso Vascular/efeitos dos fármacos , Ácidos Pentanoicos/farmacologia , Piridinas/farmacologia , Receptores de Prostaglandina/efeitos dos fármacos , Serotonina/metabolismo , Tromboxano-A Sintase/antagonistas & inibidoresRESUMO
The effects of adrenoceptor antagonists on heart rate and on arteriolar reactions to epinephrine, terbutaline, vasopressin, angiotensin II or dopamine in the rat cremaster muscle were compared using ECG analysis and quantitative intravital microscopy. Phentolamine (0.5 mg/kg i.v.) significantly reduced the vasoconstriction of arterioles elicited by topically applied epinephrine (10(-8) to 3.3 x 10(-6) M) while propranolol (0.63 mg/kg i.v.) significantly attenuated the arteriolar vasodilatation elicited by topically applied terbutaline (10(-6) to 10(-4) M). Nebivolol (0.63 mg/kg i.v.) at a dose producing a reduction of resting heart rate equivalent to that caused by propranolol modified neither the epinephrine-induced constriction nor the terbutaline-induced vasodilatation of arterioles. The arteriolar vasoconstriction induced by topically applied vasopressin (9.3 x 10(-9) M), angiotensin II (9.4 x 10(-7) M) or dopamine (5.2 x 10(-5) M) was not modified by nebivolol either. While propranolol reduced the tachycardia and hypotension induced by isoprenaline (0.025, 0.1 microgram/kg i.v.), nebivolol reduced the cardiac rhythm increase but not the blood pressure drop in response to the catecholamine (0.025, 0.1, 0.4 micrograms/kg i.v.). The present intravital microscopic study in the rat demonstrated that, at a dose exerting cardiac beta 1-adrenoceptor blockade, nebivolol is devoid of significant activity on alpha 1-, alpha 2-, beta-2-adrenoceptors and on receptors for vasopressin, angiotensin II or dopamine in resistance arterioles.
Assuntos
Agonistas Adrenérgicos/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Artérias/efeitos dos fármacos , Arteríolas/efeitos dos fármacos , Benzopiranos/farmacologia , Etanolaminas/farmacologia , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Administração Tópica , Angiotensina II/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Dopamina/farmacologia , Epinefrina/farmacologia , Injeções Intravenosas , Masculino , Músculos/irrigação sanguínea , Nebivolol , Propranolol/farmacologia , Ratos , Ratos Endogâmicos , Terbutalina/farmacologia , Fatores de Tempo , Resistência Vascular , Vasopressinas/farmacologia , Gravação em VídeoRESUMO
Changes in heart rate and in bronchomotor reactions to histamine as parameters for beta 1- and beta 2-adrenergic receptor blockade, respectively, were analyzed in anaesthetized, ventilated guinea-pigs after administration of propranolol, atenolol and nebivolol. Propranolol (0.04 to 0.63 mg/kg i.v., -15 min) produces a significant reduction of the resting heart rate (80.4 +/- 4.25 to 74.9 +/- 4.17% of premedication values; n = 8; p less than 0.05) and, at the same dose levels, a significant enhancement of the bronchoconstrictor responses to histamine (3 micrograms/kg i.v.) (129.1 +/- 6.3 to 167.7 +/- 11.2% of premedication values; n = 8; p less than 0.05). Atenolol (0.02 to 1.25 mg/kg i.v., -15 min) significantly reduces heart rates from 0.04 mg/kg on (79.4 +/- 2.6 to 69.3 +/- 3.2% of premedication value at 1.25 mg/kg; n = 8; p less than 0.05) and significantly enhances the pulmonary reaction to histamine from 0.63 mg/kg on (139.1 +/- 6.3% to 137 +/- 11.6% of premedication values at 1.25 mg/kg; n = 8; p less than 0.05), yielding a dissociation factor of 16 between the lowest cardiac active dose and the pulmonary active one. Nebivolol (0.08 to 2.5 mg/kg i.v., -15 min) significantly reduces heart rates from 0.125 mg/kg on (78 +/- 3.2% to 65.4 +/- 3.9% of premedication value at 2.5 mg/kg; n = 8; p less than 0.05) without significantly increasing pulmonary reactivity (132.2 +/- 5.4% of premedication values at 2.5 mg/kg; n = 8; p greater than 0.05), thus yielding a dissociation factor greater than 20 between cardiac-pulmonary active doses. The study demonstrates a substantial dissociation between the cardiac (beta 1-adrenoceptors) and pulmonary (beta 2-adrenoceptors) active doses of nebivolol and atenolol in comparison with propranolol in vivo.
Assuntos
Antagonistas Adrenérgicos beta/farmacologia , Atenolol/farmacologia , Benzopiranos/farmacologia , Brônquios/efeitos dos fármacos , Etanolaminas/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Histamina/farmacologia , Propranolol/farmacologia , Animais , Cobaias , Masculino , Nebivolol , Testes de Função RespiratóriaRESUMO
The effects of verapamil and of flunarizine on the epinephrine-induced vasoconstriction and on the spontaneous vasomotion of third-to-fourth-order arterioles (range 9-25 microns diameter) in the rat cremaster muscle were compared, using quantitative intravital microscopy. Verapamil as well as flunarizine [0.5 mg/kg intravenously (i.v.) in 10 s; 10-50 min postmedication] similarly reduced the submaximal arteriolar vasoconstriction induced by topically applied epinephrine (maximal concentrations 1 x 10(-7) and 1 x 10(-6) M), illustrating their inhibitory action against stimulated Ca2+ influx into vascular smooth muscle cells at the doses examined. Verapamil increased the basal arteriolar diameter (+54.6%), and reduced the frequency (-82.1%) and velocity (-65.8%) of the spontaneously cyclic changes in the diameter of arterioles, typical for the autoregulation of microcirculatory blood flow. In contrast, flunarizine slightly increased basal arteriolar diameter (+16.5%) but did not modify the pattern of spontaneous arteriolar vasomotion. The effect of verapamil and inactivity of flunarizine on the spontaneous arteriolar vasomotion may result from an interference by the former drug with the myogenic activity of vascular smooth muscle cells, caused by Ca2+ translocations in physiologic conditions and the lack of such an interference by the latter compound. These observations performed on the same blood vessels corroborate the differentiation between Ca2+ slow channel blockers (verapamil) and Ca2+ overload blockers (flunarizine) in vivo.
Assuntos
Epinefrina/farmacologia , Flunarizina/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Músculos/irrigação sanguínea , Vasoconstrição/efeitos dos fármacos , Verapamil/farmacologia , Animais , Arteríolas/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Cálcio/fisiologia , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Ratos , Ratos Endogâmicos , Fluxo Sanguíneo Regional/efeitos dos fármacos , Fatores de TempoRESUMO
Ketoconazole inhibits in vitro (IC50:2.6 X 10(-5) M) the formation of 5-HETE and LTB4 by isolated, carrageenin-elicited rat peritoneal PMN leukocytes, challenged with the Ca2+-ionophore A23187 in the presence of [14C]-arachidonic acid ([14C]-AA). The relative potency of various compounds tested in this respect is NDGA greater than nafazatrom greater than phenidone greater than ketoconazole greater than BW 755C. In contrast to the other compounds studies, ketoconazole in vitro, up to 1 X 10(-4) M, has no effect on the fatty acid cyclo-oxygenase or the 12-lipoxygenase-mediated metabolism of [14C]-AA by isolated human platelets; however, it stimulates the 15-lipoxygenase activity in phenylhydrazine-induced rabbit reticulocytes. After oral administration (10-40 mg/kg, -2 hr), ketoconazole inhibits in a dose-dependent way, the leukotriene-mediated anaphylactic bronchoconstriction in guinea pigs. This study demonstrates that ketoconazole is a comparatively specific and orally active inhibitor of the 5-lipoxygenase activity bearing on the production of leukotrienes derived from arachidonic acid.
Assuntos
Cetoconazol/farmacologia , Leucotrieno B4/biossíntese , SRS-A/biossíntese , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico , 4,5-Di-Hidro-1-(3-(Trifluormetil)Fenil)-1H-Pirazol-3-Amina , Animais , Antígenos/imunologia , Araquidonato Lipoxigenases , Ácido Araquidônico , Ácidos Araquidônicos/metabolismo , Plaquetas/metabolismo , Brônquios/efeitos dos fármacos , Catecóis/farmacologia , Inibidores de Ciclo-Oxigenase , Inibidores das Enzimas do Citocromo P-450 , Relação Dose-Resposta a Droga , Cobaias , Humanos , Ácidos Hidroxieicosatetraenoicos/biossíntese , Técnicas In Vitro , Inibidores de Lipoxigenase , Masculino , Masoprocol , Neutrófilos/metabolismo , Pirazóis/farmacologia , Coelhos , Ratos , Ratos Endogâmicos , Reticulócitos/metabolismoRESUMO
The fast intravenous injection of arachidonic acid (AA) in mice produces, in a dose-related way, mortality due to respiratory distress. Upon electron microscopical examination an extensive oedematous damage of the capillary endothelium was found; thrombotic platelet obstructions were present in a minority of pulmonary capillaries only. Protection against this toxic AA-effect is obtained with inhibitors of fatty acid cyclo-oxygenase and of thromboxane (TXA2) synthetase, suggesting involvement of TXA2 as a causative mediator. The Ca2+-entry blockers flunarizine, niludipine and nimodipine, not affecting TXA2 synthesis by murine platelets, also provide protection, but not the antiplatelet drugs ticlopidine, dipyridamole or suloctidil; thrombocytopenia induced by busulphan does not affect the AA-induced mortality nor the protection obtained with flunarizine. Platelet-independent bronchoconstriction induced by AA in guinea-pigs is also inhibited by flunarizine. This study suggests that the AA-induced mortality test reflects pulmonary conversion of AA to TXA2 producing endothelial cell damage and respiratory smooth muscle cell contraction rather than a thrombotic phenomenon. The protective effect of flunarizine against TXA2 induced changes in vivo may contribute to its effectiveness in particular hypoxic conditions associated with liberation of AA.
Assuntos
Bloqueadores dos Canais de Cálcio/farmacologia , Cinarizina/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Piperazinas/farmacologia , Tromboxano A2/farmacologia , Tromboxanos/farmacologia , Animais , Ácido Araquidônico , Ácidos Araquidônicos/toxicidade , Plaquetas/metabolismo , Brônquios/efeitos dos fármacos , Cinarizina/análogos & derivados , Inibidores de Ciclo-Oxigenase , Endotélio/efeitos dos fármacos , Flunarizina , Cobaias , Hemólise/efeitos dos fármacos , Masculino , Malondialdeído/sangue , Camundongos , Contração Muscular/efeitos dos fármacos , Músculo Liso/ultraestrutura , Músculo Liso Vascular/ultraestrutura , Receptores de Leucotrienos , Receptores de Prostaglandina/metabolismo , Risco , Tromboxano A2/antagonistas & inibidores , Tromboxano-A Sintase/antagonistas & inibidores , Fatores de TempoRESUMO
In cats, an acute thrombotic obstruction of the aorta inducing continuous platelet activation, was produced by permanent ligation above the trifurcation, temporary ligation below the caudal mesenteric artery and production of a stasis thrombus in the segment. Before, 5 min, 24 hr and 48 hr after surgery, plethysmographic systolic blood pressure in fore- and hindlegs, and clinical scoring of the hindleg function were performed; at 72 hr, venous occlusion plethysmography for quantification of blood flow was performed and collateral vascular resistance was calculated. Thrombotic occlusion resulted in a loss of adequately functioning collateral circulation as evidence by the changes in both the objective and the clinical parameters. Pre-treatment with ketanserin (1.25 mg/kg i.p. daily) significantly improved the objective circulation parameters blood pressure ratio, blood flow and collateral vascular resistance and restored the clinically scored function of post-thrombotic collateral function. Provided platelet activation contributes to human vascular pathology, a similar mechanism may be involved in the potential effect of ketanserin in man.