RESUMO
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 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)
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 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
Chronic hypoxia induces many physiological changes, but little is known about its effects on colonic epithelial function. Isolated distal colon mucosa from rats under normobaric conditions and rats submitted to hypobaric hypoxia for either 4 or 10 days was studied in an Ussing chamber. After 4 days of hypoxia, there was only a 15% increase in transepithelial resistivity. However, 10-day hypoxic rats showed higher short circuit current, potential difference, and resistivity. In this group, but not in normal or 4-day hypoxic animals, amiloride dose-dependently depressed short circuit current. The response to acute hypoxia in vitro was unchanged after chronic hypoxia and was not affected by amiloride. Although the amiloride-sensitive increase in short circuit current in 10-day hypoxic rats might resemble mineralocorticoid action, resistivity was increased and serum aldosterone was very low. It is suggested that chronic hypoxia may enhance electrogenic sodium transport by an aldosterone-independent mechanism.