Abstract
To investigate whether excessive circulating levels of atrial natriuretic factor (ANF) are responsible for orthostatic hypotension and nocturnal polyuria in patients with autonomic failure, we determined the circadian variation in the plasma concentration of ANF as well as the response of this peptide to changes in posture and extracellular fluid volume in patients with autonomic failure. We found that the plasma concentration of ANF was significantly lower in patients with autonomic failure than in controls. Patients with autonomic failure had a significantly higher urinary sodium excretion during the night (8 PM to 8 AM) than during the day (8 AM to 8 PM), and the plasma concentration of ANF significantly decreased during the night in these patients, indicating that high circulating levels of ANF were not the cause of the nocturnal natriuresis. Furthermore, circulating levels of ANF responded appropriately to reductions in right atrial pressure induced by head-up tilt and extracellular fluid volume changes induced by mineralocorticoid administration. These results indicate that exaggerated circulating levels of ANF are not responsible for the orthostatic hypotension or nocturnal natriuresis in patients with autonomic failure, and that appropriate regulation of ANF occurs in patients with autonomic failure.
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