The effect of adrenaline and noradrenaline on hormone secretion and blood flow from the thyroid vein in sheep with exteriorized thyroids

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Abstract
Emotional stimulus to the sheep has previously been shown to cause increased thyroid hormone secretion; the influence of adrenaline [epinephrine] and noradrenaline [norepinephrine] in this process has been investigated. Sheep bearing exteriorized thyroid glands on carotid-artery-jugular vein loops were used. Thyroid vein blood was collected through a cannula in the jugular vein within the loop, and blood flow was measured by a plethysmographic technique. I131 (50[mu]c) was injected intramuscularly (I.M.) into the sheep, and 4-7 days later the concentration of total and protein bound I131 in thyroid vein blood was measured in samples taken every 10 min for 4 hr. Intra-carotid injections of 1 [mu]g, I.V. injections of 5 [mu]g,or I.V. infusions at 10 [mu]g/min for 10 min, of epinephrine or epinephrine were administered 1.5 hr after commencement of sampling. Blood flow from the thryoid was measured in similar experiments. No significant changes in thyroid hormone secretion could be attributed to epinephrine or norepinephrine and it was concluded that circulating catecholamines do not influence the release of thyroid hormone observed after brief emotional stimulus in the sheep.