[Neurohormones coming from the normal and tumoral human anterior pituitary. Secretion and regulation in vitro].

Several neuropeptides, classically associated with the hypothalamus have been found in the anterior pituitary and their local synthesis has been hypothesized. Using normal and tumoral human pituitaries we found in the tissue itself different neuropeptides (TRH, SRIH, GHRH) and dopamine in variable quantities according to the nature of the tissue. They were all present in normal pituitaries while only stimulatory neurohormones like TRH and GHRH were found in tumoral tissue implying an imbalance between the stimulatory and inhibitory control of hypophyseal hormones (PRL and GH) in pituitary adenomas. Fragments from normal pituitaries and dispersed cells from GH, PRL and nonsecreting adenomas, were perifused for 4 hours in a Krebs-Ringer medium collected every 2 min and GH, PRL, TRH, GHRH and SRIH were measured by RIA under basal conditions and in the presence of 10(-6) mol/L DA, TRH or SRIH. Neuropeptides and DA were characterized by HPLC. Both normal and tumoral pituitaries released TRH, SRIH and GHRH in large amounts suggesting their local synthesis. There was an in situ regulation between SRIH and GH as their secretion profile was negatively correlated, GH secretion decreasing while SRIH secretion was increasing. Moreover the release of TRH was stimulated 5 to 20 folds by DA, while PRL decreased at the same time. Pulses of TRH and SRIH had differential effects on GHRH and SRIH release according to the nature of the tissue as TRH stimulated SRIH release from normal pituitary while it inhibited SRIH release from adenoma. These results indicate that anterior pituitary cells can release neuropeptides which are probably endogenously synthesized and have a local regulation.(ABSTRACT TRUNCATED AT 250 WORDS)