Context: Urocortin 1 (Ucn1) and urocortin 3 (Ucn3)/stresscopin are new members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn1 binds to both CRF type 1 (CRF1) and type 2 receptors (CRF2), whereas Ucn3 is a specific agonist for CRF2. Recently, direct involvement of the locally synthesized CRF family in adrenocortical function has been proposed.
Objective, design, and setting: We examined in situ expression of Ucn and CRF receptors in nonpathological human adrenal gland and its disorders using immunohistochemistry and mRNA in situ hybridization.
Results: Ucn immunoreactivity was localized in the cortex and medulla of nonpathological adrenal glands. Ucn1 immunoreactivity was marked in the medulla, whereas Ucn3 was immunostained mostly in the cortex. Both CRF type 1 and CRF2 were expressed in the cortex, particularly in the zonae fasciculata and reticularis but very weakly or undetectably in the medulla. Immunohistochemistry in serial tissue sections with mirror images revealed that both Ucn3 and CRF2 were colocalized in more than 85% of the adrenocortical cells. mRNA in situ hybridization confirmed these findings above. In fetal adrenals, Ucn and CRF receptors were expressed in both fetal and definitive zones of the cortex. Ucn and CRF receptors were all expressed in the tumor cells of pheochromocytomas, adrenocortical adenomas, and carcinomas, but its positivity was less than that in nonpathological adrenal glands, suggesting that Ucn1, Ucn3, and CRF receptors were down-regulated in these adrenal neoplasms.
Conclusions: Ucn1, Ucn3, and CRF receptors are all expressed in human adrenal cortex and medulla and may play important roles in physiological adrenal functions.