title: Interactive effect of aging and local muscle heating on renal vasoconstriction during isometric handgrip.
abstract: The purpose of the study was to determine the interactive effect of aging and forearm muscle heating on renal vascular conductance and muscle sympathetic nerve activity (MSNA) during ischemic isometric handgrip. A tube-lined, water-perfused sleeve was used to heat the forearm in 12 young (27 +/- 1 yr) and 9 older (63 +/- 1 yr) subjects. Ischemic isometric handgrip was performed before and after heating. Muscle temperature (intramuscular thermistor) was 34.3 +/- 0.2 and 38.7 +/- 0.1 degrees C during normothermia and heating, respectively. At rest, heating had no effect on renal blood velocity (Doppler ultrasound) or renal vascular conductance in either group (young, n = 12; older, n = 8). Heating compared with normothermia caused a significantly greater increase in renal vasoconstriction during exercise and postexercise muscle ischemia (PEMI) in both groups. However, the increase in renal vasoconstriction during heating was greater in the older compared with the young subjects (18 +/- 3 vs. 8 +/- 3%). During handgrip, heating elicited greater increases in MSNA responses in the older group (young, n = 12; older, n = 6), whereas no statistical difference was observed between groups during PEMI. In summary, aging augments renal vascular responses to ischemic isometric handgrip during heating of the exercising muscle. The greater renal vasoconstriction was associated with augmented MSNA in the older subjects.
authors.affiliation: Heart and Vascular Institute and Department of Cellular and Molecular Physiology, General Clinical Research Center, Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033-2390, USA.
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Kuipers
authors.forename: Charity L
authors.initials: CL
authors.lastname: Sauder
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Kearney
authors.forename: Chester A
authors.initials: CA
authors.lastname: Ray
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001831:Body Temperature; D005260:Female; D005542:Forearm; D018737:Hand Strength; D006339:Heart Rate; D006801:Humans; D007036:Hypothermia, Induced; D007511:Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation / Q000503:physiopathology*; D010465:Perception; D010543:Peroneal Nerve / Q000503:physiopathology; D005082:Physical Exertion; D012077:Renal Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012079:Renal Circulation; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013997:Time Factors; D018608:Ultrasonography, Doppler; D014661:Vasoconstriction