Effects of norepinephrine infusion on rectal temperature, plasma free fatty acids (FFA) concentration and its turnover rate were studied in rats treated chronically with norepinephrine, thyroxine, or both. Chronic treatments with these hormones resulted in greater increases in rectal temperature and FFA turnover rate in response to norepinephrine as compared with the alterations in controls. Norepinephrine-induced elevation of FFA concentration was smaller in norepinephrine-treated and norepinephrine plus thyroxine-treated rats than in controls, and in thyroxine-treated rats the elevation was similar to that of controls. The regression coefficient of FFA concentration of its turnover rate was greater in all the treated groups than in controls although positive correlations were observed among both variables in the former and the latter. From the results it was inferred that the greater increase in removal of plasma FFA was produced by norepinephrine in parallel with the greater increase in rectal temperature by norepinephrine in rats treated with norepinephrine or thyroxine than in the controls. The effects of norepinephrine infusion were also studied in surgically thryoidectomized rats. In thyroidectomized rats adapted to warm or cold, the smaller increases in rectal temperature and ithe turnover rate of plasma FFA were induced by norepinephrine as compared with the changes in intact rats. The alterations in FFA concentration produced by norepinephrine were less in warm-adapted thyroidectomized rats and greater in cold-acclimated thyroidectomized rats than in respective controls.

Animals↗

PubMed1975

[Lung retention of metallic fumes. (I) The inhalation apparatus of metallic fume for rats (author's transl)].

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Aerosols↗

PubMed1975

[Effect of acute cold exposure on blood composition in rats treated with 6-Hydroxydopamine (author's transl)].

Rats injected with 6-hydroxydopamine (6-OHDA) into the lateral ventricle showed greater elevation in plasma FFA and beta-hydroxybutyrate and significant decrease in blood sugar and lactate following acute cold exposure at -10 degrees C for 2 hours. Changes in the blood composition induced by the cold exposure in rats treated with 6-OHDA intravenously were not different from those observed in control rats. Adrenomedullectomized rats treated with 6-OHDA responded to the cold exposure with rather marked elevation in plasma FFA and beta-hydroxybutyrate. These results were discussed from the view-point of compensatory changes in metabolic regulation in the absence of norepinephrine.

Adrenal Medulla↗

PubMed1975

[Role of thyroid hormone in cold adaptation. 1. Requirement of thyroxine during the course of cold acclimation as estimated by noradrenaline sensitivity (author's transl)].

The amount of thyroxine required for the development and maintenance of cold acclimation was investigated in the rat. Warm-adapted thyroidectomized rats could not survive at 5 degrees C. When thyroxine was replaced, these rats could survive and responded to noradrenaline with increased oxygen consumption in proportion to the dose of replaced thyroxine. Judged from the amount of thyroxine in thyroidectomized rats necessary to restore noradrenaline sensitivity to the same level as seen in intact controls, 30 degrees C-adapted rats were found to require 3.3 mug thyroxine/100 g b.w./day, while 5 degrees C-adapted rats required only 1.2 mug. It is concluded that the amount of thyroxine necessary to produce cold acclimation is much larger than that for the maintenance of cold acclimation.

Acclimatization↗

PubMed1975

[Role of thyroid hormone in cold adaptation. 2. Increase of food consumption and fecal excretion of thyroxine during cold exposure (author's transl)].

In order to clarify the relationship between food consumption and excretion of thyroxine during cold exposure, 131I-thyroxine was injected to 1w- and 3w-cold exposed rats and the radioactivity of 131I in the feces and urine was counted over the first 24 hr and the next same period of time following the injection. The percentage of a dose of radioactive thyroxine excreted into the feces over the first 24 hr was the highest in 1w-cold exposed rats, whereas in 3w-cold exposed rats the excretion of radioactive thyroxine did not differ from the values in warm adapted rats. Since the correlation curve between fecal excretion of thyroxine and fecal weight was linearly positive and food consumption increased during the early stage of cold exposure, larger fecal thyroxine observed in the first week after cold exposure was inferred to be result from increased food consumption as well as fecal volume in this period. Nevertheless, since the increment of fecal excretion of thyroxine in 1w-cold exposed rats was only 30% as compared with the value of control group, it is impossible to explain 2-3 fold increase in thyroxine requirement during early stage of cold exposure by the increase in fecal excretion of thyroxine.

Acclimatization↗

PubMed1974