Assuntos
Glândulas Suprarrenais/metabolismo , Catecolaminas/metabolismo , Etanol/farmacologia , Sistema Nervoso Simpático/fisiologia , Glândulas Suprarrenais/efeitos dos fármacos , Glândulas Suprarrenais/inervação , Animais , Denervação , Dopamina beta-Hidroxilase/metabolismo , Epinefrina/metabolismo , Humanos , Masculino , Norepinefrina/metabolismo , Feniletanolamina N-Metiltransferase/metabolismo , Ratos , Síndrome de Abstinência a Substâncias/metabolismo , Fatores de Tempo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Since thyroid hormones influence urinary excretion of catecholamines after exposure to cold, the effects of hyper- and hypo-thyroidism on adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2), phenylethanolamine-N-methyl transferase (PNMT) (EC 2.1.1.28), and serum dopamine-beta-hydroxylase (DbetaH) (EC 1.14.17.1) of rats of 23 and 4 degrees C were studied. TH changes resembled the urinary excretion pattern at 4 degrees C in being higher after 8 days than after 1 day of exposure, and in declining as acclimation occurred. At 23 degrees C, TH activity of hypothyroid rats was significantly higher than in euthyroid or hyperthyroid animals, and after 1 day at 4 degrees C the value increased even more. While in the hypothyroid animals at 4 degrees C the concentration of adrenal catecholamines was less, the epinephrine to norepinephrine ratio was higher than at 23 degrees C. Very high TH activity with a decline in catecholamine concentration suggests that the capacity of TH had been exceeded. PNMT activity was significantly elevated in this group. TH activity was not decreased in the hyperthyroid group at 23 degrees C, and was increased after 8 days at 4 degrees C, suggesting that circulating thyroid hormones have no direct inhibitory effect on TH. Serum DbetaH was elevated after exposure to 4 degrees C, regardless of thyroid hormonal status. The activation of adrenal TH in hypothyroid rats at 23 degrees C and of TH, PNMT, and serum DbetaH at 4 degrees C is probably the result of increased activity of the sympathetic nervous system.
Assuntos
Glândulas Suprarrenais/metabolismo , Catecolaminas/metabolismo , Temperatura Baixa , Hormônios Tireóideos/fisiologia , Glândulas Suprarrenais/enzimologia , Animais , Dopamina beta-Hidroxilase/sangue , Epinefrina/metabolismo , Hipertireoidismo/metabolismo , Hipotireoidismo/metabolismo , Masculino , Norepinefrina/metabolismo , Tamanho do Órgão , Feniletanolamina N-Metiltransferase/metabolismo , Ratos , Hormônios Tireóideos/sangue , Hormônios Tireóideos/metabolismo , Tireoidectomia , Fatores de Tempo , Tirosina 3-Mono-Oxigenase/metabolismoAssuntos
Temperatura Baixa , Músculos/metabolismo , Miocárdio/metabolismo , Norepinefrina/metabolismo , Hormônios Tireóideos/fisiologia , Animais , Peso Corporal/efeitos dos fármacos , Coração/efeitos dos fármacos , Hipertireoidismo/metabolismo , Hipotireoidismo/metabolismo , Técnicas In Vitro , Cinética , Masculino , Metimazol/farmacologia , Músculos/efeitos dos fármacos , Tamanho do Órgão/efeitos dos fármacos , Ratos , Tireoidectomia , Tiroxina/farmacologia , Fatores de TempoRESUMO
Exposure of rats to an ambient temperature of 5 degrees C for 4 to 6 weeks led to a 30 to 80 percent increase in the rate of oxygen consumption and a 50 percent increase in the rate of ethanol oxidation by liver slices, a 50 percent increase in mitochondrial alpha-glycerophosphate oxidase activity of liver, and a 100 percent increase in Na++K+-activated adenosine-triphosphatase, activity. Ouabain, an inhibitor of the Na++K+-activated adenosine-triphosphatase, completely blocked the extra respiration and ethanol oxidation. Dinitrophenol, which increases oxygen consumption and ethanol oxidation by liver slices from normal rats, was ineffective with slices from cold-exposed animals. Ethanol disappearance rate in vivo was also increased by cold acclimation, even though liver alcohol dehydrogenase activity was reduced. It is suggested that increased hydrolysis of ATP by the sodium pump system is responsible for the increased oxygen consumption and ethanol metabolism in the livers of cold-acclimated animals.
