RESUMO
In order to study the probable physiological role of non-activated lymphocytes on islet B-cells, we incubated and perfused rat pancreatic islets in the presence of low (2.8 mM) and high (16.7 mM) glucose concentrations after pre-exposure for 60 min to rat lymphocytes or to substances secreted by lymphocytes. Insulin secretion and 86Rb+, 45Ca2+ and [3H]-phosphoinositide metabolite fluxes were lower compared to controls when islets were pre-exposed to lymphocytes but were not different when islets were pre-exposed to substances secreted by lymphocytes. These alterations in isotope flux suggest that, when lymphocytes and islets are in contact, closure of potassium channels and a paradoxical effect of glucose load on insulin release occur in the presence of low glucose concentrations. The alterations observed are probably due to a swift and direct action of lymphocyte secretion perhaps induced by a direct of islet cells.
Assuntos
Insulina/metabolismo , Linfócitos/metabolismo , Animais , Secreção de Insulina , Ilhotas Pancreáticas , Masculino , RatosRESUMO
In order to study the probable physiological role of non-activated lymphocytes on islet B-cells, we incubated and perfused rat pancreatic islets in the presence of low (2.8 mM) and high (l6.7 mM) glucose concentrations after pre-exposure for 60 min to rat lymphocytes or to substances secreted by lymphocytes. Insulin secretion and 86Rb+, 45Ca2+ and [3H]-phosphoinositide metabolite fluxes were lower compared to controls when islets were pre-exposed to lymphocytes but were not different when islets were pre-exposed to substances secreted by lymphocytes. These alterations in isotope flux suggest that, when lymphocytes and islets are in contact, closure of potassium channels and a paradoxical effect of glucose load on insulin release occur in the presence of low glucose concentrations. The alterations observed are probably due to a swift and direct action of lymphocyte secretion perhaps induced by a direct contact of islet cells.
Assuntos
Ratos , Animais , Masculino , Técnicas In Vitro , Insulina/fisiologia , Insulina/metabolismo , Linfócitos/fisiologia , Ilhotas PancreáticasRESUMO
The effect of exercise training (ET) on renal sympathetic nerve activity (RSNA), baroreflex control of RSNA and heart rate (HR), and arterial pressure (AP) responsiveness to phenylephrine and angiotensin II (ANG II) was studied in six trained (T) and six sedentary (S) male Wistar rats. ET was performed on a motor treadmill for 13 wk. The RSNA signals of unanesthetized rats were processed by an analog-to-digital converter to quantify the nerve discharges associated with changes in AP and HR. The reflex control of RSNA and HR were evaluated during progressive injections of phenylephrine and sodium nitroprusside. Mean arterial pressure (MAP) was similar in both groups. RSNA was significantly lower in T rats (28 +/- 2 vs. 36 +/- 3%). T rats had an impairment of baroreflex control of RSNA in response to nitroprusside (4.9 +/- 0.89 vs. 12.3 +/- 1.2 bars.cycle-1.mmHg-1). ET decreased AP responsiveness for phenylephrine and ANG II. Therefore ET produces 1) no change in resting MAP but a significant decrease in RSNA and AP responsiveness and 2) partial impairment of baroreflexes, i.e., bradycardic responses and RSNA during MAP decrease.
Assuntos
Pressão Sanguínea , Rim/inervação , Condicionamento Físico Animal , Pressorreceptores/fisiologia , Reflexo/fisiologia , Sistema Nervoso Simpático/fisiologia , Angiotensina II/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Masculino , Nitroprussiato/farmacologia , Fenilefrina/farmacologia , Pressorreceptores/efeitos dos fármacos , Ratos , Reflexo/efeitos dos fármacosRESUMO
During cycloergometric exercise at progressively increasing loads, blood lactate concentration increased about 12-fold. Pyruvate concentration decreased initially (for loads of 50-75 W), increased with loads of 75 to 125 W and then decreased again until the end of exercise. The malate concentration increased abruptly between 50 and 75 W, followed by a slow decline; citrate increased about nine-fold as the exercise load was increased to 125 W and then fell sharply. Thus, the production of lactate during low-intensity exercise seems to occur by the "mass-action effect" caused by enhanced glycolysis, whereas with moderate loads the glycolysis rate is very much reduced and most of the lactate production seems to involve the action of the malate-aspartate shuttle. For high-intensity exercise, both mechanisms appear to participate in lactate production.
Assuntos
Exercício Físico , Lactatos/sangue , Cromatografia Líquida de Alta Pressão , Citratos/sangue , Humanos , Lactatos/metabolismo , Malatos/sangue , Masculino , Músculos/metabolismo , Consumo de Oxigênio , Piruvatos/sangueRESUMO
During cycloergometric exercise at progressively increasing loads, blood lactate concentration increased about 12-fold. Pyruvate concentration decreased initially(for loads of 50-75 W), increased with loads of 75 to 125 W and then decreased again until the end of exercise. the malate concentration increased abruptly between 50 and 75 W, followed by a slow decline; citrate increased about nine-fold as the exercise load was increased to 125 W and then fell sharply. Thus, the production of lactate during low-intensity exercise seems to occur by the "mass-action effect" caused by enhanced glycolysis, whereas with moderate loads the glycolysis rate is very much reduced and most of the lactate production seems to involve the action of the malate-aspartate shuttle. For high-intensity exercise, both mechanisms appear to participate in lactate production
