Magnitude and variability of blood pressure and renal vascular conductance responses to postural changes, exercise, and cold exposure in healthy adults

OBJECTIVE: Constriction of vascular smooth muscle cells evokes a counterbalancing dilatory signal from endothelium, a phenomenon called feedback vasodilation. Ex vivo studies have identified nitric oxide and endothelium-derived hyperpolarizing factor as key signals mediating feedback vasodilation. However, to study this mechanism in vivo, we need non-invasive approaches to quantify responses to vasoconstrictive stimuli in humans. We hypothesized that standing, hand grip exercise, or cold exposure would raise blood pressure (BP) in healthy volunteers. METHODS: BP was recorded continuously with theHuman Non-Invasive BP Nano (ADInstruments) while three vasoconstrictive stimuli were performed: standing from a supine position, isometric hand grip exercise, and immersion of one hand in cold water. Renal artery Doppler ultrasound was performed with the exercise and cold stimuli. The primary outcome measures were the changes in BP and renal vascular conductance (RVC, velocity/BP) before and after each stimulus. Data are presented as mean ± standard error. Repeated measures one-way ANOVA with Dunnett’s post hoc test was used to compare BP during stimulation against baseline. To assess inter-day reproducibility, each visit was repeated at least 48 hours later, and paired t-test and Pearson’s correlation were applied. RESULTS: 9 participants (6 women and 3 men) aged 30.2 ± 5.2 years participated. On first visits, standing from supine raised systolic BP by 12.1 ± 3.0 mmHg (p = 0.0065) and diastolic BP by 13.2 ± 1.7 mmHg (p < 0.0001). Handgrip at 100% effort raised systolic BP by 15.2 ± 4.6 mmHg (p = 0.0445) and diastolic BP by 11.5 ± 2.5 mmHg (p = 0.0098). Handgrip decreased RVC by 0.26 ± 0.06 cm/s/mmHg (p = 0. 0119) during systole and by 0.24 ± 0.07 cm/s/mmHg (p = 0.0591) during diastole. Cold exposure increased systolic BP by 29.4 ± 3.9 mmHg (p = 0.0002) and diastolic BP by 24.7 ± 2.8 mmHg (p < 0.0001). Cold decreased RVC by 0.42 ± 0.09 mmHg (p = 0.0065) during systole and by 0.33 ± 0.11 mmHg (p = 0.0464) during diastole. While the BP and RVC responses were similar from visit one to visit two at a group level, intra-individual correlations were not statistically significant. CONCLUSIONS: Standing, exercise, and cold each induced vasoconstriction in healthy volunteers as demonstrated by increases in BP and decreases in RVC. The magnitude and variation of these responses, along with inter-day differences, facilitate sample size estimation for studies to investigate medical, genetic, or pharmacologic determinants of feedback vasodilation in humans. Funded by the Intramural Research Program of the National Institutes of Allergy and Infectious Diseases. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.