Antidiuretic hormone response to volume depletion in diabetic patients with cardiac autonomic dysfunction

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Abstract
Insulin-independent diabetic patients (39) were separated into 2 groups from the results of 3 different tests for cardiac vagal neuropathy: heart rate response to deep breathing, Valsalva maneuver and heart rate response to postural change. Patients (17) were considered as without (''intact'' patients) and 16 as with (''denervated'' patients) cardiac autonomic dysfunction. One patient with a transplanted heart was also studied. Plasma antidiuretic hormone (ADH), plasma aldosterone and plasma renin activity (PRA) were measured immediately before and 60 min after i.v. administration of frusemide and passage from lying to standing. The kinetics of hormonal responses were analyzed more precisely (5 blood collections) in 6 patients of each group who were studied again. Heart rate and blood pressure were recorded before each blood collection. Volume depletion estimated from the rise in plasma protein (+11.9 and +12.2% in ''denervated'' and ''intact'' patients respectively) and heart rate response (+10.6 and +14.7%) were similar in both groups. Mean blood pressure was unchanged in the ''intact'' patients whereas it fell in the ''denervated'' patients (-13.5%). PRA (+161.5 and +231.2% in ''denervated'' and ''intact'' patients respectively) and plasma aldosterone (+318.2 and 279%) increased in both groups whereas plasma ADH was stimulated only in ''intact'' patients (+55.3%). The failure of ADH to respond significantly to the volume stimulus in ''denervated'' patients was confirmed by the results of the timecourse study. Plasma ADH remained at the same levels in ''denervated'' patients whereas it increased significantly (+82.4%) in ''intact'' patients. There was no ADH response in the transplanted patient. In humans, cardiac receptors and vagal pathways play a role in ADH response to volume depletion.