Comparative effects of verapamil and volume overload on atrial natriuretic factors and the renin-angiotensin aldosterone-vasopressin system

The authors compared the effects of verapamil (120mg three times daily for 3 days) with those of acute volume expansion with normal saline on the plasma levels of atrial natriuretic factors (ANF), renin (PRA), angiotensin II (AII), aldosterone (ALD), and arginine-vasopressin (AVP) in healthy subjects. A randomized, double-blind, placebo-controlled study of crossover design was employed, where each individual received two acute volume overloads 1 week apart, one during placebo and the other during treatment with verapamil. Verapamil reduced blood pressure (BP) and increased the plasma levels of ANF, PRA, AII, ALD, and AVP. Strong positive correlations were observed between PRA, AII, ALD, and AVP, but not with ANF. Acute volume expansion (1500mL saline in 15 minutes, in supine legs-up position) similarly to verapamil increased ANF levels; however, opposite to verapamil, it reduced PRA-AII-ALD, did not modify AVP levels, and increased BP. The mechanisms of these changes are discussed. In verapamil-treated subjects, volume expansion produced an additional increase in ANF and inhibited the PRA-AII-ALD axis, suggesting that in young healthy individuals, verapamil does not interfere with the reflex compensatory hormonal mechanisms activated under circumstances of acute volume-salt overload, with rapid expansion of the central vascular compartment. Our study indicates that verapamil and volume expansion represent two different stimuli for ANF secretion associated with opposite changes in the PRA-AII-ALD axis. In addition verapamil can be used as a tool to study and understand the simultaneous increases in ANF and in PRA, AII, ALD, and AVP, characteristics of congestive heart failure.