Expression and regulation of melanocortin receptor-5 (MC5-R) in the bovineadrenal cortex

Among the five members of the melanocortin receptor (MC-R) family, MC2 and MC5 are expressed in peripheral tissues. The receptor MC2 (ACTH receptor) a lmost exclusively expressed in the adrenal cortex whereas MC5-R is expresse d in several organs including the adrenal cortex. Both receptors bind ACTH and activate adenylate cyclase. The aim of this work was to study the spati al distribution of MC5-R among the different zones of the bovine adrenal co rtex and to analyze the regulation of its expression by its own ligands, AC TH and alpha-MSH and by angiotensin II (AII). Using semi-quantitative rever se transcriptase-polymerase chain reaction (RT-PCR) analysis and RNase prot ection assay, MC5-R was detected only in the glomerulosa zone whereas MC2-R was present in both glomerulosa and fasciculata zones of adult adrenal cor tex. Treatments by ACTH, alpha-MSH, or AII increased the MC5-R mRNA level i n glomerulosa cells by factors 7, 5, and 4.5, respectively. However, althou gh potentially regulated by hormones, MC5-R is expressed at a level at leas t 100 times less than MC2-R, suggesting that MC5-R expression might only be at trace levels in grown adults, but could be much higher during embryogen esis. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.