Corticotropin-Releasing Factor Binding to Peripheral Tissue and Activation of the Adenylate Cyclase-Adenosine 3′,5′-Monophosphate System

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Abstract
Specific binding sites for rat corticotropin-releasing factor (rCRF) are present in rat adrenal medulla, ventral prostate, spleen, liver, kidney and testis and bovine chromaffin cells in culture. Maximal binding of [125I]rCRF occurred within 25 min at 4.degree. C and was saturable. Scatchard analysis of rCRF binding to rat adrenal membranes and bovine chromaffin cells revealed the existence of 2 classes of binding sites. One class had a relatively higher apparent affinity and lower number of binding sites; the other class had a relatively lower affinity and higher number of binding sites. CRF induced a dose-related increase in rat adrenal membrane adenylate cyclase activity and cAMP levels in bovine chromaffin cells. nM concentrations of rCRF maximally stimulated adenylate cyclase activity in rat adrenal membranes and maximally increased cAMP levels in bovine chromaffin cells to 86% and 130% above control values, respectively. The demonstration of specific CRF-binding sites in a variety of peripheral tissues and the finding that activation of specific CRF-binding sites in adrenal tissue stimulates the adenylate cyclase-cAMP system suggest that CRF may have an important regulatory role in various peripheral tissues.