Localization of ACTH receptor mRNA by in situ hybridization in mouse adrenal gland

Stimulation of steroidogenesis in the adrenal cortex is a major physiological action of adrenocorticotropic hormone (ACTH). This action is presumed to be mediated by the ACTH receptor and is functionally connected with the hypothalamus-pituitary-adrenal axis. To gain information concerning the distribution of the ACTH receptor in this axis, we examined mRNA for the ACTH receptor in the adrenal gland, pituitary and hypothalamus of the mouse, by using in situ hybridization. The Y-1 mouse adrenal tumour cell line was also examined. The specific hybridization signal for ACTH receptor mRNA was uniformly distributed in the Y-1 cells, although the level of expression was low. The adrenal cortex showed a strong signal for the ACTH receptor mRNA in both the zona fasciculata and the zona glomerulosa, sites that are involved in the mediation of the action of ACTH on the synthesis and release of glucocorticoids and aldosterone. In the zona reticularis of the cortex, a small number of cells showed positive hybridization signals. Moreover, a few scattered cells were positive in the adrenal medulla. In contrast, the hybridization results for both the hypothalamus and the pituitary proved to be negative. These results indicate that the mouse ACTH receptor is a peripheral receptor that is exclusively located in the adrenal gland.