Expression of ACTH receptors (MC2-R and MC5-R) in the glomerulosa and the fasciculata-reticularis zones of bovine adrenal cortex.

The recent cloning of a family of melanocortin receptors (MC-R) has identif ied five distinct G protein- and adenylate cyclase-coupled receptors. The M C2-receptor (MC2-R) preferentially binds ACTH. It is expressed in the adren al cortex and is hence considered to be the ACTH receptor. The MC5-receptor (MCS-R) binds ACTH and alpha-MSH and is more widely expressed. The aim of this work was to study the sites of MC5-R expression in the bovine adrenal cortex and to compare the regulation of the expression of MC2-R and MC5-R i n bovine adrenocortical cells in primary culture. Analysis of the expressio n of MC5-R was obtained by RT-PCR, using total RNA purified from glomerulos a and fasciculata zones of bovine adrenocortical tissue. MC5-R expression c ould be detected in RNA from the glomerulosa zone but was undetectable in t he fasciculata zone. in bovine adrenocortical cells in culture, ACTH stimul ates MC5-R expression in the glomerulosa and fasciculata cells. A DNA fragm ent, was obtained using primers based on the bovine ACTH receptor (MC2-R) s equence. This fragment was detected in RNA from the two zones. The probe wa s used to quantify MC2-R by Ribonuclease Protection assay and we observed t hat MC2-R mRNA is 3.6-fold more abundant in glomerulosa than in fasciculata -reticularis cells.