title: Aging augments renal vasoconstrictor response to orthostatic stress in humans.
abstract: 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.
authors.affiliation: Pennsylvania State University College of Medicine, Hershey, Pennsylvania; and.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Clark
authors.affiliation: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Monahan
authors.affiliation: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania rdrew1@hmc.psu.edu.
authors.forename: Rachel C
authors.identifier: http://orcid.org/0000-0001-8001-1946
authors.initials: RC
authors.lastname: Drew
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D062186:Arterial Pressure; D017704:Baroreflex; D001783:Blood Flow Velocity; D004244:Dizziness / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D007668:Kidney / Q000098:blood supply* / Q000294:innervation*; D008150:Lower Body Negative Pressure; D008297:Male; D008875:Middle Aged; D012079:Renal Circulation; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance; D014661:Vasoconstriction; D055815:Young Adult
keywords: aging; baroreflex; orthostasis; renal vasoconstriction; sympathetic nervous system