PITUITARY ADENYLATE CYCLASE-ACTIVATING PEPTIDE-38 (PACAP)-38 IS RELEASED INTO HYPOPHYSEAL PORTAL BLOOD IN THE NORMAL-MALE AND FEMALE RAT

Pituitary adenylate cyclase activating polypeptide (PACAP) was first i solated from ovine hypothalamus as two molecular forms, the basic 38 r esidue amidated peptide PACAP-38 and the N-terminal 27 amino acid sequ ence PACAP-27. A dense plexus of PACAP immunoreactive fibres is presen t in the internal and external layers of the median eminence and in ot her parts of the hypothalamus with PACAP cell bodies in the paraventri cular and supraoptic nuclei. The present study shows, for the first ti me, that, as assessed by radioimmunoassay of extracted plasma, the amo unt of PACAP-38 in hypophysial portal is significantly greater than in peripheral blood, and that as assessed by reversed phase high perform ance liquid chromatography, PACAP 1-38 is the major form in portal blo od. This evidence is crucial for the fact that PACAP-38 may be a hypot halamic-pituitary regulatory factor.