Characterization of human and rat glucagon-like peptide-1 receptors in the neurointermediate lobe: Lack of coupling to either stimulation or inhibition of adenylyl cyclase

F. Satoh, S. A. Beak, C. J. Small, M. Falzon, M. A. Ghatei, S. R. Bloom, D. M. Smith

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

Glucagon-like peptide-1 (GLP-1) has been shown to bind to the posterior pituitary in the rat. We examined GLP-1 binding sites in human postmortem and rat pituitaries. Dense [125I]GLP-1 binding was seen in both human and rat posterior pituitary. In rat neurointermediate lobe membranes the binding site showed a Kd of 0.2 ± 0.01 nM and a binding capacity of 600 ± 33 fmol/mg protein (n = 3). In human pituitary membranes the binding site showed a Kd of 0.82 ± 0.05 nM and a binding capacity of 680 ± 93 fmol/mg protein (n = 3). Chemical cross-linking showed a relative mol wt for the receptor-ligand complex of 73,100 ± 1,400 (n = 3) in man and 59,300 ± 900 (n = 3) in rat. GLP-1 (1 μM) failed to increase cAMP levels measured in rat neurointermediate lobes, whereas pituitary adenylate cyclase-activating polypeptide (100 nM) increased cAMP from a basal level of 14 ± 1 to 80 ± 4 pmol/neurointermediate lobe. 15 min (n = 5; P < 0.01). GLP-1 (up to 1 μM) did not affect the pituitary adenylate cyclase-activating polypeptide-stimulated cAMP levels. GLP-1 (up to 1 μM) also did not stimulate release of vasopressin or oxytocin from isolated rat neurointermediate lobes. The posterior pituitary shows the highest density of GLP-1-binding sites yet seen, but their function and signal transduction mechanism remain unknown.

Original languageEnglish
Pages (from-to)1301-1309
Number of pages9
JournalEndocrinology
Volume141
Issue number4
DOIs
Publication statusPublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology

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