Presence of tyrosine-hydroxylase activity in anterior pituitary adenomas and ectopic anterior pituitaries in male rats.

There is evidence for local regulatory effects of dopamine (DA) and norepinephrine (NE) on the release of prolactin (PRL) and other hormones from the anterior pituitaries transplanted to an ectopic site. In order to further explore these suspected regulatory mechanisms and to determine if they may exist also in pituitary tumors, we have examined the activity of tyrosine-hydroxylase (TH) in ectopic pituitaries and in hyperplastic pituitaries of estrogen-treated rats. Adult male rats with a pituitary graft in each kidney and sham-operated controls were examined 5 weeks after surgery. Rats implanted for 3 months with Silastic capsules containing diethylstilbestrol (DES) or with empty capsules were used 10 weeks after the capsules were removed. TH activity in ectopic anterior pituitaries of grafted rats was significantly higher than that measured in the eutopic anterior pituitaries of control animals. Similarly, TH activity was significantly higher in DES-induced pituitary tumors than in control pituitaries. These data support the possible existence of local catecholaminergic mechanism(s) that could be modulating PRL secretion from pituitary tumors and from ectopic pituitaries.