Investigation and characterization of receptors for pituitary adenylate cyclase-activating polypeptide in human brain by radioligand binding and chemical cross-linking

Journal Article · Wed May 01 00:00:00 EDT 1991 · Journal of Clinical Endocrinology and Metabolism; (USA)

DOI:https://doi.org/10.1210/jcem-72-5-958· OSTI ID:5546003

Suda, K; Smith, D M; Ghatei, M A; Murphy, J K; Bloom, S R ^[1]

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1. Hammersmith Hospital, London, (United Kingdom)

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel peptide of hypothalamic origin which increases adenylate cyclase activity in rat anterior pituitary cell cultures. The 38-amino acid peptide shows a close sequence homology to vasoactive intestinal peptide (VIP). Binding sites for PACAP in membranes from postmortem human brain tissue were studied using ({sup 125}I)PACAP27 as the radioligand. High specific binding sites (amount of specific binding measured at 0.25 nM ({sup 125}I)PACAP27 in femtomoles per mg protein +/- SEM; n = 4) were present in hypothalamus (344.5 +/- 13.0), brain stem (343.0 +/- 29.3), cerebellum (292.0 +/- 21.1), cortex (259.6 +/- 19.8), and basal ganglia (259.2 +/- 50.3). Specific binding sites in pituitary, although present, were less abundant (35.0 +/- 8.9). Binding of ({sup 125}I)PACAP27 was reversible and time, pH, and temperature dependent. Despite the homology with VIP, VIP was a poor inhibitor of ({sup 125}I)PACAP27 binding (IC50, greater than 1 microM) compared with PACAP27 (IC50, 0.5-1.3 nM) and PACAP38 (IC50, 0.2-1.3 nM). Scatchard plots of ({sup 125}I)PACAP27 binding showed the presence of both high and lower affinity sites. Chemical cross-linking of PACAP-binding sites revealed that ({sup 125}I)PACAP27 was bound to polypeptide chains of 67,000 and 48,000 mol wt. Thus, we have demonstrated the presence of PACAP-specific receptors in human brain which are not VIP receptors. This opens the possibility of PACAP functioning as a novel neurotransmitter/neuromodulator in human brain.

• OSTI ID: 5546003
• Journal Information: Journal of Clinical Endocrinology and Metabolism; (USA), Journal Name: Journal of Clinical Endocrinology and Metabolism; (USA) Vol. 72:5; ISSN JCEMA; ISSN 0021-972X
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CROSS-LINKING
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MAMMALS
MAN
MEMBRANE PROTEINS
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDES
PITUITARY GLAND
POLYMERIZATION
POLYPEPTIDES
PRIMATES
PROTEINS
RADIOASSAY
RADIOISOTOPES
REACTION KINETICS
REAGENTS
RECEPTORS
TRACER TECHNIQUES
VERTEBRATES