PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE, HELOSPECTIN, AND VASOACTIVE INTESTINAL POLYPEPTIDE IN HUMAN CORPUS CAVERNOSUM

1 The distribution and effects of pituitary adenylate cyclase-activati ng polypeptide (PACAP-27 and -38), helospectin (Hel-1 and Hel-2), and vasoactive intestinal polypeptide (VIP), were investigated in isolated preparations of human corpus cavernosum (CC). 2 Immunohistochemistry revealed coinciding profiles of nerve structures that showed immunorea ctivities for VIP and PACAP, and VIP and Hel. Confocal microscopy show ed the co-existence of VIP- and PACAP-immunoreactivities, and VIP- and Hel-immunoreactivities in most (90%) varicose nerve structures. 3 As determined by radioimmunoassay, the amounts of VIP, PACAP-27, and PACA P-38 in the preparations were 61.7 +/- 11.6, 0.1 +/- 0.05, and 3.7 +/- 0.5 pmol g(-1) wet weight of tissue (pmol g(-1) wet wt), respectively . In tissue from patients with diabetes, the content of VIP was lower (13.7 +/- 0.5 pmol g(-1) wet wet wt), whereas that of PACAP (-27 and - 38) was unchanged. 4 Cyclic nucleotide levels were determined in prepa rations exposed to PACAP-27, PACAP-38, Hel-l, Hel-2, and VIP. Ah the p eptides, but Hel-2, significantly increased the concentrations of cycl ic AMP, whereas the levels of cyclic GMP were unchanged. 5 The peptide s concentration-dependently relaxed noradrenaline-contracted preparati ons. The order of potency was VIP > PACAP 27 > Hel-1 > Hel-2 > PACAP-3 8. 6 Hel-1, VIP and PACAP-27 effectively counteracted electrically ind uced contractions. At 10(-6) M, the highest peptide concentration used , the inhibitory effects obtained reached 96 +/- 3%, 87 +/- 6%, and 80 +/- 3%, respectively. 7 The results suggest that PACAP and Hel-1 are co-localized with VIP in nerve structures within the human cavernous t issue, and that the peptides are effective relaxants of CC preparation s ipl vitro. The role of the investigated peptides for penile erection remains to be established.