Regulation of PAMP and adrenomedullin receptor expression in the rat adrenal zona glomerulosa

Two peptide hormones are produced from the precursor peptide pre-proadrenoemdullin, known to be expressed in rat zona glomerulosa cells. Receptors for both adrenomedullin and pro-adrenomedullin N-terminal 20 peptide (PAMP) have been identified in the rat adrenal cortex but there is no information to date about the regulation of expression of these receptors, and the significance of these peptides in the regulation of adrenocortical function. In the present study the effects of dietary sodium changes on PAMP and adrenomedullin receptor expression was investigated. Feeding rats a low sodium diet resulted in a decrease in both PAMP and adrenomedullin binding in the zona glomerulosa. Adrenomedullin specific binding was 378 fmol/mg protein in the controls and 89 fmol/mg protein following dietary sodium depletion. PAMP binding was 288 fmol/mg protein in controls and 110 fmol/mg protein in the low sodium group. These data do not support a role for these peptides in the response of the adrenal zona glomerulosa to sodium depletion. It is possible that these peptides may, like ACTH, have acute stimulatory, but long-term inhibitory actions on the zona glomerulosa.