Effect of adrenomedullin infusion on basal and stimulated aldosterone secretion in conscious sheep with cervical adrenal autotransplants

In vivo and in vitro studies have shown conflicting effects of adrenomedull in (ADM) on the secretion of steroid hormones from the adrenal gland. While some investigators report no effect of this peptide on the output of vario us hormones, others have reported both stimulatory and inhibitory roles for ADM. We have shown that basal aldosterone secretion rate (ASR), ill consci ous sheep with cervical adrenal autotransplants, did not change when ADM wa s infused directly into the adrenal arterial supply. While not affecting ba sal ASR, ADM did produce pronounced increases in adrenal blood flow (DF). T his elevation of BF in association with ADM infusion was seen in all subseq uent experiments. When aldosterone output was acutely stimulated by angiote nsin II (AngII), potassium chloride (KCl) and adrenocorticotrophic hormone (ACTH), ADM was seen to drastically reduce the secretion of aldosterone wit h all agonists studied. After pre-exposure to ADM, all three agonists incre ased ASR but the magnitude of the responses were somewhat blunted. ADM did not have the same effect on cortisol secretion stimulated by ACTH, suggesti ng that the ability of this peptide to influence adrenal gland function is limited to the zona glomerulosa. In conditions of chronic elevation of aldo sterone levels, such as in Na deficiency, ADM did not display the same inhi bitory abilities seen in the acute stimulation experiments. Hence, ADM has been shown to have a direct, inhibitory role on the acute stimulation of al dosterone by AngII, KCI and ACTH while not affecting basal or chronic aldos terone secretion or cortisol secretion stimulated by ACTH.