Interaction of ovine pituitary adenylate cyclase-activating peptide (PACAP-38) with rat lung membranes

Peptides. May-Jun 1993;14(3):621-7. doi: 10.1016/0196-9781(93)90154-9.

Abstract

The binding of ovine pituitary adenylate cyclase-activating peptide (PACAP-38) to rat lung membranes was investigated using [125I]PACAP-38 as radioligand. Binding was rapid at 37 degrees C, reversible, saturable, and time, concentration, and temperature dependent. Kinetic parameters derived from saturation experiments revealed a Kd = 100 +/- 15 pM, Bmax = 310 +/- 36 fmol/mg protein, and a Hill slope factor (nH) of 1.17 +/- 0.12. Various chemically synthesized analogues of PACAP-38, as well as related peptides, were tested for their ability to displace [125I]PACAP-38. Of those that had an IC50 < 0.2 microM, the following order of potency was determined: PACAP-38 (IC50 = 25 nM) > or = [Ile2]PACAP-38 (IC50 = 31 nM) > PACAP-27 (IC50 = 54 nM) > [Tyr1]PACAP-38 (IC50 = 104 nM) > GHRH(1-29)NH2 (IC50 = 108 nM) > PHI (IC50 = 181 nM) > [Ser2]PACAP(2-38) (IC50 = 198 nM). Glucagon, PHM, secretin, and GIP exhibited little affinity in the same binding assay. Vasoactive intestinal peptide (VIP) had an IC50 in excess of 1 microM. When [125I]VIP was used as radioligand, PACAP-27 had an IC50 = 0.2 nM > PACAP-38 (IC50 = 0.5 nM) > VIP (IC50 = 16 nM). A novel analog of PACAP-38, [4-Cl-D-Phe6,Leu17]PACAP-38, was able to displace [125I]VIP very efficiently (IC50 = 1 nM), but had little potency in displacing [125I]PACAP-38 (IC50 = 320 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Lung / metabolism*
  • Male
  • Membranes / metabolism
  • Neuropeptides / metabolism*
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Radioligand Assay
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Cell Surface / metabolism*
  • Receptors, Gastrointestinal Hormone / metabolism
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Pituitary Hormone*
  • Receptors, Vasoactive Intestinal Peptide
  • Sheep
  • Vasoactive Intestinal Peptide / metabolism

Substances

  • Adcyap1 protein, rat
  • Neuropeptides
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Cell Surface
  • Receptors, Gastrointestinal Hormone
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Pituitary Hormone
  • Receptors, Vasoactive Intestinal Peptide
  • Vasoactive Intestinal Peptide