Changes in the catecholamine metabolism in the adrenal medulla of male hamsters with experimental hyperprolactinemia.

1. Prolactin (PRL) can play a role as a physiological modulator of adrenal medulla function in several rodents. 2. We have examined the effects of hyperprolactinemia induced by ectopic pituitary grafts in Syrian hamsters on the adrenal medulla contents of catecholamines (CA) and their metabolites, as well as on the activities of several enzymes involved in the metabolism of these amines. 3. Increases in the peripheral levels of PRL in these animals were associated with decreases in adrenal medulla weight and increases in adrenal medulla contents of norepinephrine, epinephrine and vanilmandelic acid, the main degradative metabolite of CA, while adrenal medulla contents of the O-methylated derivatives of CA, normetanephrine and metanephrine, were unaltered. 4. These changes were correlated with increases in the adrenal medulla activity of monoamine oxidase, while the activities of tyrosine hydroxylase, phenylethanolamine-N-methyl transferase and catechol-O-methyl transferase were unaltered. 5. These results indicate that PRL is able to act on the adrenal medulla of hamsters by increasing the ability of these cells to metabolize CA via oxidative deamination.