TYROSINE-HYDROXYLASE ACTIVITY AND CATECHOLAMINE BIOSYNTHESIS IN THE ADRENAL-MEDULLA OF RATS DURING STRESS

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  • 1 January 1985
    • journal article
    • research article
    • Vol. 233  (1) , 32-38
Abstract
Chronic hypertension and hypoglycemia are known to increase the capacity for catecholamine biosynthesis in the rat adrenal medulla by increasing the maximal velocity of the rate-limiting enzyme, tyrosine hydroxylase (TH). The gradual increase in maximal TH activity is preceded by a more rapid increase in the affinity of TH for its pterin cofactor. These short-term alterations in adrenal TH activity were related to the severity of the stress, associated with parallel changes in catecholamine biosynthesis, and prevented by prior adrenal denervation. Cold exposure, which leads to comparable long-term increases in adrenal TH activity, did so without causing a prior activation of TH. Adrenal TH was activated by acute cold exposure if the sympathetic nerves, that normally are stimulated during cold, are destroyed previously by 6-hydroxydopamine treatment. Alterations in adrenal TH activity vary according to the type and duration of physiological stress, and may be mediated by temporally distinct processes.