| Abstract: | Rat adrenal gland levels of dopamine beta-hydroxylase are subject to dual control. Activation of the splanchnic nerves to the adrenal medulla by reserpine induces the synthesis of dopamine beta-hydroxylase without altering the rate of enzyme degradation. In contrast, hypophysectomy causes a decline in steady state dopamine beta-hydroxylase levels by first accelerating the rate of degradation, then by slowing the rate of enzyme synthesis as well. Adrenocorticotropic hormone administration partially reversed the effect of hypophysectomy on dopamin beta-hydroxylase degradation. These findings suggest that the trans-synaptic factors controlling dopamine beta-hydroxylase induction act by a different mechanism (enzyme synthesis) than the hormonal controls regulating steady state levels (enzyme degradation). Thus, active inhibition of enzyme degradation may be an important control in maintenance of steady state enzyme levels. |
