Background: In Dahl salt sensitive rats, the “air puff stress” increases blood pressure (BP) and is associated with acute renal sodium (Na) retention. This study revealed increased dietary potassium (K) may abolish stress induced Na retention. Our human studies have shown the mental stress (MS) of playing a video game increases BP in youths, but the effect on Na excretion is bimodal. Retainers (NaR), retain Na with MS while excreters (NaE), excrete Na during MS. A greater increase in BP with a prolonged effect is seen in NaR. This stress induced NaR phenomena can be abolished by Ang II blockage. Because BP effects of Na intake are closely related to K intake, this study sought to compare UNaV and UKV before and after MS between NaE and NaR.
Methods: We compared parallel changes in UNaV, UKV, aldosterone (aldo), and Ang II in response to 1 hour of MS in 90 healthy youths (16-19 years) after a 3 day Na/K controlled diet. We compared NaE (n=64) to NaR (n=26).
Results: The change in UNaV (5.5mEq±0.6SEM vs. -3.4mEq±0.7SEM; p=<0.001), UKV (2.1mEq±0.3SEM vs. 0.4mEq±0.2SEM; p=0.002), aldo (-15.4 pg/mL ±5.3SEM vs. 3.7 pg/mL ±7.9SEM; p=0.055) and Ang II (0.4 pg/mL ±0.7SEM vs. 4.9pg/mL±3.6SEM; p=0.085) was greater in NaE vs NaR, as seen in the figure. Similarly, both groups had a baseline UNaV/UKV ratio of 4:1, which changed during stress to 2:1 in NaR and 3:1 in NaE.
Conclusion: MS in normotensive youths has remarkably different effects on UNaV and UKV. Salt sensitive animal models have shown K supplementation may reverse Na retention in response to MS. This study suggests K supplementation may reverse the Na/K ratio to pre-stress conditions. Figure: Delta value comparison between NaE & NaR in UNaV, UKV, aldo, & Ang II.