OPIOID AND TACHYKININ NEUROPEPTIDES IN PROLACTIN-SECRETING HUMAN PITUITARY-ADENOMAS

Two opioid neuropeptides, methionine enkephalin (ME) and P-endorphin ( BE), and one tachykinin neuropeptide, substance P (SP), were quantifie d in 10 prolactin (PRL)-secreting human pituitary adenomas and in 10 c ontrol human pituitaries. Immunohistochemical techniques provided appr opriate staining for PRL. Reversed-phase high performance liquid chrom atography (RP-HPLC) was used to purify these three neuropeptides befor e their analysis, radioimmunoassay (RIA) was used for the quantificati on of SP-like immunoreactivity (SP-LI), and liquid secondary-ion mass spectrometry (LSIMS) was used for the qualitative and quantitative ana lysis of ME and a tryptic peptide of BE. This study shows that, for 90 % of the cases studied here (excluding one hypothyroidism case), the t achykinin A neuropeptide SP-LI level is decreased, the POMC peptide BE level is not altered, and the proenkephalin A neuropeptide ME level i s increased in these PRL-secreting tumors.