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Properties and regulation of high-affinity pituitary receptors for corticotropin-releasing factor

Authors
Journal
Biochemical and Biophysical Research Communications
0006-291X
Publisher
Elsevier
Publication Date
Volume
110
Issue
2
Identifiers
DOI: 10.1016/0006-291x(83)91192-0

Abstract

Abstract Specific receptors for corticotropin-releasing factor (CRF) were identified in the rat anterior pituitary gland by binding studies with 125I-Tyr-CRF. Binding of the labeled CRF analog to pituitary particles was rapid and temperature-dependent, and reached steady state within 45 min at 22°C. The CRF binding sites were saturable and of high affinity, with dissociation constant (Kd) of 0.76 × 10 −9 M. Pituitary binding of 125I-Tyr-CRF was inhibited by CRF, Tyr-CRF and the active 15–41 fragment of CRF, but not by the inactive 21–41 CRF fragment and unrelated peptides. The binding-inhibition potencies of the CRF peptides were similar to their activities as stimuli of adrenocorticotropic hormone (ACTH) release. The high-affinity CRF sites were markedly reduced in adrenalectomized rats, and this change was reversed by dexamethasone treatment. These data indicate that the high-affinity CRF sites demonstrated in the anterior pituitary are the functional receptors which mediate the stimulatory action of the peptide on ACTH release, and that CRF receptors are down-regulated during increased secretion of the hypothalamic hormone.

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