RESUMO
This study examined the metabolic mechanisms involved in the impaired insulin secretion by pancreatic islets isolated from fasted and exercised rats. Insulin secretion to glucose (8.3 to 16.7 mM) stimulus was lower in fasted (F), exercised (E), and fasted plus exercised (EF) rats as compared with the control group. The rate of glucose oxidation by isolated islets was reduced in F and EF rats, but it was not modified in the E group. In response to alpha-KIC (5, 10, 15, and 20 mM), insulin secretion was not different in EF and F rats, in comparison to controls, except in the E group, which showed values slightly higher. These findings suggest that changes in insulin secretion in fasted rats, associated or not to exercise training, might be a consequence of a reduced activity of the right-hand side of the Krebs cycle (from pyruvate to oxoglutarate), leading to decreased glucose oxidation. However, the exercise itself caused a significant decrease of insulin secretion without altering glycolysis and Krebs cycle activities.
Assuntos
Glicemia/metabolismo , Metabolismo Energético/fisiologia , Jejum/fisiologia , Insulina/fisiologia , Ilhotas Pancreáticas/fisiologia , Esforço Físico/fisiologia , Animais , Ciclo do Ácido Cítrico/fisiologia , Técnicas de Cultura , Masculino , Perfusão , Ratos , Ratos Wistar , Taxa Secretória/fisiologiaRESUMO
To investigate the alterations in insulin secretion induced by habituation to single daily meal, adult rats were trained on a regular-fasting scheme (2-hr feeding/22-hr fasting) for 4 weeks. Insulin secretion induced by nutrient secretagogues (D-glucose and L-leucine) and the rates of 45Ca2+ outflow and 14C-glucose oxidation were studied in isolated islets obtained from these animals and in fed and 22-hr single-fasted rats. As expected, in the 22-hr fasted group, insulin secretion was drastically decreased although not abolished while 45Ca2+ outflow and 14C-glucose oxidation rates were only partially reduced. However, the regular-fasted rats did not secrete insulin in response to the nutrient secretagogues; calcium entry was not detected although a partial reduction in 14C-glucose oxidation rate was observed. These results suggest that regular fasting induces alterations in pancreatic B-cell glycolytic pathways leading to impairment of calcium efflux and insulin secretion. Such impairment is more pronounced than that induced by a single 22-hr fast.
Assuntos
Jejum , Privação de Alimentos/fisiologia , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Animais , Cálcio/metabolismo , Relação Dose-Resposta a Droga , Glucose/metabolismo , Glucose/farmacologia , Insulina/análise , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Leucina/farmacologia , Masculino , Ratos , Ratos Endogâmicos , Fatores de TempoRESUMO
A rotating wheel cage for rats which permits voluntary physical activity and free access to food and water is described. The cyclometer is entirely mechanical and does not require an external energy source. The apparatus can be constructed from commercially available, inexpensive components.
Assuntos
Ingestão de Líquidos , Ingestão de Alimentos , Abrigo para Animais , Atividade Motora , Animais , Masculino , Ratos , Ratos Endogâmicos , Restrição FísicaRESUMO
A rotating wheel cage for rats which permits voluntary physical axtivity and free access to food and water is decribed. The cyclometer is entirely mechanical and does not requiere an external energy source. The apparatus can be constructed from commercially available, inexpensive components