ADRENAL ORIGIN OF PLASMA CATECHOLAMINES AFTER DECAPITATION: A STUDY IN NORMAL AND DIABETIC RATS

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Abstract
The concentrations of catecholamines and the activities of dopamines‐hydroxylase were measured in blood obtained from decapitated diabetic and aged‐matched control rats. The activity of dopamines‐hydroxylase in blood from diabetic rats was much greater (5 fold) than that seen for control rats. For both diabetic and control rats, decapitation was accompanied by an increase in levels of adrenaline and noradrenaline with no change in the activity of plasma dopamines‐hydroxylase. The results are consistent with a predominantly adrenal origin of catecholamines and extra‐adrenal origin of dopamine‐β‐hydroxylase. The high activity of dopamines‐hydroxylase in diabetes indicates either an increased activity of the sympathetic nervous system or changes in dopamines‐hydroxylase turnover.