RESUMO
The present study was designed to examine the effects of a sesquiterpene lactone isolated from Artemisia douglasiana Besser (dehydroleucodine), a xanthanolide sesquiterpene isolated from Xanthium cavanillesii Schouw (xanthatin) and a semisynthetic butenolide (3-benzyloxymethyl-5H-furan-2-one) on mast cell degranulation induced by compound 48/80. Peritoneal mast cells from male adult Sprague-Dawley rats were purified in Percoll, preincubated in the presence of test lactones (dehydroleucodine, xanthatin or 3-benzyloxymethyl-5H-furan-2-one) and then challenged with the mast cell activator compound 48/80 (10 microg/ml). Concentration-response and kinetic studies of mast cell serotonin release evoked by compound 48/80, evaluation of mast cell viability and morphology by light and electron microscopy, and comparative studies using ketotifen and sodium chromoglycate were carried out. Serotonin release studies, carried out together with morphological studies, showed the effectiveness of the above lactones to stabilize mast cells. The comparative study with ketotifen and sodium chromoglycate, well known mast cell stabilizers, showed the following order of potency dehydroleucodine=xanthatin>3-benzyloxymethyl-5H-furan-2-one> or =ketotifen/sodium chromoglycate to inhibit mast cell serotonin release induced by compound 48/80. The present study provides the first strong evidence in favour of the hypothesis that dehydroleucodine, xanthatin and 3-benzyloxymethyl-5H-furan-2-one inhibit compound 48/80-induced serotonin release from peritoneal mast cells, acting thus as mast cell stabilizers. Our findings may provide an insight into the design of novel pharmacological agents which may be used to regulate the mast cell response.
Assuntos
Antiulcerosos/farmacologia , Degranulação Celular/efeitos dos fármacos , Lactonas/farmacologia , Mastócitos/efeitos dos fármacos , p-Metoxi-N-metilfenetilamina/farmacologia , Animais , Antiulcerosos/química , Corantes/metabolismo , Relação Dose-Resposta a Droga , Processamento de Imagem Assistida por Computador , Lactonas/química , Masculino , Mastócitos/ultraestrutura , Estrutura Molecular , Peritônio/citologia , Ratos , Ratos Sprague-Dawley , Serotonina/metabolismo , Cloreto de Tolônio/metabolismoRESUMO
Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 +/- 2.2 microm; their resting parameters were: membrane potential 23.8 +/- 0.8 mV; total membrane specific resistance 519.1 +/- 94.6 ohms.cm2, and specific capacity 0.99 +/- 0.03 microF.cm(-2). Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.
Assuntos
Interações Espermatozoide-Óvulo/fisiologia , 4-Aminopiridina/farmacologia , Animais , Cricetinae , Eletrofisiologia , Feminino , Técnicas In Vitro , Masculino , Potenciais da Membrana , Mesocricetus , Microscopia Eletrônica de Varredura , Oócitos/efeitos dos fármacos , Oócitos/fisiologia , Oócitos/ultraestrutura , Técnicas de Patch-Clamp , Bloqueadores dos Canais de Potássio/farmacologia , Interações Espermatozoide-Óvulo/efeitos dos fármacosRESUMO
Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 µm; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 µF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try
Assuntos
Masculino , Cobaias , Animais , Feminino , Bloqueadores dos Canais de Potássio/farmacologia , Fertilização/fisiologia , Mesocricetus , Oócitos , Oócitos/fisiologia , Oócitos/ultraestrutura , Técnicas de Patch-Clamp/veterináriaRESUMO
Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 Am; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 AF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try(AU)
Assuntos
Masculino , Cobaias , Animais , Feminino , Oócitos/ultraestrutura , Oócitos/efeitos dos fármacos , Oócitos/fisiologia , Técnicas de Patch-Clamp/veterinária , Bloqueadores dos Canais de Potássio/farmacologia , Fertilização/fisiologia , MesocricetusRESUMO
Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 Am; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 AF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try(AU)