Short- and long-term changes in adrenal tyrosine hydroxylase activity during insulin-induced hypoglycemia and cold stress.

Insulin-induced hypoglycemia increases the capacity for catecholamine biosynthesis in the rat adrenal medulla by two temporally distinct processes: a rapid increase in the affinity of tyrosine hydroxylase (TH) for cofactor and a more gradual increase in the maximal TH activity. Cold exposure leads to comparable long-term increases in adrenal TH activity, apparently without causing a prior activation of TH.