Key result
Older age augmented the renal vasoconstrictor response to orthostatic stress, with a greater increase in renal vascular resistance during -30 mmHg LBNP compared to young subjects (20% vs 6%; P<0.05).
Why the study?
Does healthy aging affect the renal vasoconstrictor response to orthostatic stress in humans?
Cross-Sectional (n=20)
Does healthy aging affect the renal vasoconstrictor response to orthostatic stress in humans?
Healthy aging augments the renal vasoconstrictor response to orthostatic stress, suggesting an altered sympathetically mediated mechanism to maintain blood pressure.
May heighten orthostatic intolerance risk in older adults; extends age-related renal vascular insights but leaves clinical relevance open.
The ability of the human body to maintain arterial blood pressure (BP) during orthostatic stress is determined by several reflex neural mechanisms. Renal vasoconstriction progressively increases during graded elevations in lower body negative pressure (LBNP). This sympathetically mediated response redistributes blood flow to the systemic circulation to maintain BP. However, how healthy aging affects the renal vasoconstrictor response to LBNP is unknown. Therefore, 10 young (25 ± 1 yr; means ± SE) and 10 older (66 ± 2 yr) subjects underwent graded LBNP (-15 and -30 mmHg) while beat-to-beat renal blood flow velocity (RBFV; Doppler ultrasound), arterial BP (Finometer), and heart rate (HR; electrocardiogram) were recorded. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as mean BP/RBFV. All baseline cardiovascular variables were similar between groups, except diastolic BP was higher in older subjects (P < 0.05). Increases in RVR during LBNP were greater in the older group compared with the young group (older: -15 mmHg Δ10 ± 3%, -30 mmHg Δ20 ± 5%; young: -15 mmHg Δ2 ± 2%, -30 mmHg Δ6 ± 2%; P < 0.05). RBFV tended to decrease more (P = 0.10) and mean BP tended to decrease less (P = 0.09) during LBNP in the older group compared with the young group. Systolic and diastolic BP, pulse pressure, and HR responses to LBNP were similar between groups. These findings suggest that aging augments the renal vasoconstrictor response to orthostatic stress in humans.
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Clark et al. (2015) conducted a cross-sectional in Healthy aging (n=20). Older age vs. Young age was evaluated on Increase in renal vascular resistance (RVR) during -30 mmHg lower body negative pressure (p=< 0.05). Older age augmented the renal vasoconstrictor response to orthostatic stress, with a greater increase in renal vascular resistance during -30 mmHg LBNP compared to young subjects (20% vs 6%; P<0.05).
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