Background: We hypothesized that stress-induced increases in Ang-II would increase the retained sodium load over the course of a day in a significant percentage of African-Americans (AAs).
Methods: We tested this hypothesis with a double blind placebo-controlled trial which examined the effect of an angiotensin receptor antagonist blocker (irbesartan) on the pressure natriuresis response to one hour of mental stress induced by a competitive video game task in 93 healthy, normotensive AAs with a mean age of 26 years. The 3-hour protocol consisted of a 1-hour stress period preceded and followed by a 1-hour rest period. Blood and urine were collected hourly and blood pressure at 15 minute intervals. The subjects were divided into those who increased (excreters, upper panel) or decreased (retainers, lower panel) UNaV with stress in the placebo condition.
Results: The ARB increased the change in UNaV during stress by 10.2 mEq, or approximately 235 mgs in Retainers but had no effect in Excreters. The ARB also had a beneficial effect on the blood pressure levels in Retainers but not Excreters, lowering levels throughout the protocol in this group.
Conclusions: Assuming 4 episodes of stress during a day, the additional sodium load induced by Ang II would be approximately 1,000 mgs, which would increase the average intake by an estimated one third. From a prevention perspective, these individuals would need to reduce their sodium intake by a third to compensate for the amount of sodium reabsorbed during episodes of mental stress throughout the day.
Figure. Effect of angiotensin receptor blocker on sodium excretion (UnaV) in response to stress in AA excreters vs. retainers.