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Influence of thyroid hormone on the nitrogen excretion and the resistance of goldfish, Carassius auratus, to anoxia Redlich, Aline Berta


Daily determinations on the nitrogen exoretion in thyroid-treated goldfish and subsequent death by anoxia showed that thyroxin immersion caused a high initial rise in the nitrogen excretion. This is presumably due to metabolism of available protein. This rise was followed by a sharp drop, during which carbohydrates and fats are probably utilized. A second lower peak in nitrogen excretion was registered later, probably due to general tissue breakdown, similar to starvation symptoms. The relative height of the peaks varied with the dose of hormone given. While lower doses and high temperature elevated the nitrogen excretion, higher doses tended to depress it. Desiccated thyroid feeding also had a rather depressive action. The anoxia experiments showed that the higher the dose of the hormone, the longer were the fish able to survive over untreated controls. It was concluded that thyroid treatment increases metabolism in goldfish, which is not accompanied by a raised oxygen consumption as in mammals but by an adaptation to lower oxygen tensions, anaerobic metabolism and respiration. This adaptation seems to increase in efficiency with increasing dose of thyroid hormone.

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