Up-regulation of adrenal cortical and medullary atrial natriuretic peptideand gene expression in rats with deoxycorticosterone acetate-salt treatment

Our previous study demonstrated that human adrenal medulla is a site of atr ial natriuretic peptide (ANP) synthesis. To further evaluate the role of ad renal ANP in body fluid homeostasis, we investigated the changes in adrenal ANP in rats receiving deoxycorticosterone acetate (DOCA)-salt treatment. I n situ hybridization and immunohistochemical study showed that adrenal ANP messenger RNA (mRNA) and ANP-like immunoreactivities (AhTP-LI) were mainly localized in the zona glomerulosa and medulla of vehicle-treated rats. DOCA -salt treatment activated ANP mRNA and peptide expression in all adrenal zo nes, especially in the zona fasciculata/reticularis from 12 h to the entire 8-day study period. Using a semi-quantitative RT-PCR technique, the relati ve quantities of ANP mRNA in the adrenals of the DOCA-salt-treated group we re significantly increased from 1 to 8 days, whereas the adrenal weights of DOCA-salt-treated rats were significantly decreased from day 2 to day 8. O ur results are the first to indicate that ANP is synthesized not only in th e adrenal medulla but also in the adrenal cortex and their syntheses are ma rkedly increased in DOCA-salt-treated rats. These results imply that adrena l ANP may participate in the intraadrenal regulation of adrenal function on water-electrolyte homeostasis in an autocrine or paracrine manner.