Receptors for calcitonin gene-related peptide (CGRP) in the rat adrenal cortex

We previously demonstrated the presence of adrenomedullin receptors in the rat adrenal cortex. There is evidence, however, that the actions of adrenom edullin may also be mediated by the CGRP receptor. The present study was de signed to determine whether specific CGRP receptors are present in the rat adrenal cortex. Adrenal glands were, sectioned and immunostained with a pri mary antibody raised against the first intracellular loop of the CGRP-1 rec eptor. Staining was visualised using alkaline phosphatase and vector red. I mmunostaining for the CGRP-I receptor was found in the zona glomerulosa and the adrenal medulla, but not in the inner adrenocortical zones. ACTH treat ment caused an increase in staining intensity in the glomerulosa. Ligand bi nding studies suggested the existence of two populations of CGRP binding si tes, one with a Kd of 0.1 nM, the second of 37 nM. Only CGRP-I and adrenome dullin displaced labeled CGRP binding. These results suggest that the CGRP- I receptor is expressed in the adrenal zona glomerulosa and that a second c lass of binding site is also present. The CGRP-I receptor appears to be reg ulated by ACTH.