The effect of chronic iron deficiency on adrenal tyrosine hydroxylase activity.

Chronic nutritional iron deficiency of 2 to 5 weeks duration reduced the blood hemoglobin content to 30-50% of control values and resulted in an increase in rat adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2) activity. Kinetic and mixing experiments indicated that this increase was due to an increase in enzyme protein. The body weight of iron-deficient rats ranged from 60 to 80% of control; this factor, however, was not responsible for the increase in adrenal TH as enzyme activity was directly proportional to final body weight. To determine whether the increase in adrenal TH in iron-deficient rats was due to increased sympathetic activity to the adrenal medulla, the splanchnic nerve was cut. The increased TH was still observed after adrenal denervation; this indicates that the mechanism of response to iron deficiency lies within the adrenal itself. Age of the rats is important in determining whether the increase in TH activity will occur.