Lack of rapid aldosterone effects on forearm resistance vasculature in health

Objectives Systemic infusions of aldosterone cause an acute increase in systemic vascular resistance (SVR) in healthy subjects. It is not clear whether this is due to a direct effect on the vasculature or the result of increased sympathetic tone. We investigated the short-term effects of locally infused aldosterone on the forearm resistance bed. Methods In this dose response study, we assessed the effects of incremental doses (10, 50, 100 ng/minute) of intrabrachial aldosterone on forearm blood flow (FBF), using conventional strain gauge plethysmography. Arterial blood pressure was monitored continuously, using finger photoplethysmography. Forearm vascular resistance (FVR) was calculated. FBF and FVR were also measured in the non-infused arm. Changes in FBF and FVR in the infused arm were corrected for those occurring in the control arm. Results Plasma aldosterone levels in the venous effluent of the infused arm increased in a dose-dependent fashion, from 113.3+/-17.9 pg/ml at baseline to 297.8+/-51.8 pg/ml at 10 ng/minute (p=<0.01), 743.9+/-105.9 pg/ml at 50 ng/min (p=<0.001 vs. baseline) and 1230.6+/-73.7 pg/ml at 100 ng/min (p=<0.0005 vs. baseline). Plasma concentrations of aldosterone in the control arm did not change significantly vs. baseline. The corrected FBF (+4.1+/-10.3%) and corrected FVR (+4.3+/-11.3%) did not change significantly even at peak infusion rates. Conclusions Local intra-arterial infusion of aldosterone had no acute effect on forearm resistance vessels in healthy male volunteers.