Effect of hypothyroidism on responsiveness to β-adrenergic stimulation

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Abstract
Chronic administration of aminotriazole (0.5 g/kg food) to rats was accompanied by a reduced responsiveness to acute administration of the β-adrenergic agonist, l-isoproterenol (50–100 μg/kg, sc). The responses tested included water intake, change in heart rate in the anesthetized and unanesthetized rat, change in mean blood pressure, and change in blood glucose concentration. In addition, the increase in tail skin temperature accompanying administration of epinephrine (1 mg/kg, sc) was significantly reduced in the hypothyroid group. Administration of l-thyroxine (25 μg/kg per day, ip) to aminotriazole-treated rats prevented the reduction in responsiveness to β-adrenergic stimulation. Thus, an interaction appears to exist between the level of thyroid activity and responsiveness to β-adrenergic agonists in rats.