Abstract
Immunohistochemical staining of dopamine-β-hydroxylase (DβH) in the lamb adrenal medulla, using antibodies conjugated to horseradish peroxidase, has provided morphologic evidence that reserpine initially causes a depletion of DβH protein followed by recovery within a week of the enzyme content. This corroborates biochemical evidence that increased reflex stimulation of the medulla by reserpine produces a loss of DβH through exocytosis of chromaffin vesicles and that recovery is due to synthesis rather than activation of the enzyme. The ultrastructural changes observed were consistent with recent findings that chromogranins are synthesized by ribosomes in the endoplasmic reticulum and incorporated into vesicles in the Golgi apparatus. The changes in catecholamine and DβH staining were not uniform throughout the medulla but were most marked in the epinephrine-containing cells near the corticomedullary junction where the cholinesterase staining was densest. This is consistent with biochemical evidence that synthesis and release of the enzyme are under both neural and hormonal control.