title: Muscle mechanoreflex activation via passive calf stretch causes renal vasoconstriction in healthy humans.
abstract: Reflex renal vasoconstriction occurs during exercise, and renal vasoconstriction in response to upper-limb muscle mechanoreflex activation has been documented. However, the renal vasoconstrictor response to muscle mechanoreflex activation originating from lower limbs, with and without local metabolite accumulation, has not been assessed. Eleven healthy young subjects (26 ± 1 yr; 5 men) underwent two trials involving 3-min passive calf muscle stretch (mechanoreflex) during 7.5-min lower-limb circulatory occlusion (CO). In one trial, 1.5-min 70% maximal voluntary contraction isometric calf exercise preceded CO to accumulate metabolites during CO and stretch (mechanoreflex and metaboreflex; 70% trial). A control trial involved no exercise before CO (mechanoreflex alone; 0% trial). Beat-to-beat renal blood flow velocity (RBFV; Doppler ultrasound), mean arterial blood pressure (MAP; photoplethysmographic finger cuff), and heart rate (electrocardiogram) were recorded. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as MAP/RBFV. All baseline cardiovascular variables were similar between trials. Stretch increased RVR and decreased RBFV in both trials (change from CO with stretch: RVR - 0% trial = Δ 10 ± 2%, 70% trial = Δ 7 ± 3%; RBFV - 0% trial = Δ -3.8 ± 1.1 cm/s, 70% trial = Δ -2.7 ± 1.5 cm/s;P< 0.05 for RVR and RBFV). These stretch-induced changes were of similar magnitudes in both trials, e.g., with and without local metabolite accumulation, as well as when thromboxane production was inhibited. These findings suggest that muscle mechanoreflex activation via passive calf stretch causes renal vasoconstriction, with and without muscle metaboreflex activation, in healthy humans.
authors.affiliation: Penn State Heart and Vascular Institute, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania rachel.drew@umb.edu.
authors.forename: Rachel C
authors.identifier: 0000-0001-8001-1946
authors.initials: RC
authors.lastname: Drew
authors.affiliation: Penn State Heart and Vascular Institute, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Blaha
authors.affiliation: Penn State Heart and Vascular Institute, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Herr
authors.affiliation: Penn State Heart and Vascular Institute, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
authors.forename: Ruda
authors.initials: R
authors.lastname: Cui
authors.affiliation: Penn State Heart and Vascular Institute, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
authors.forename: Lawrence I
authors.initials: LI
authors.lastname: Sinoway
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D007537:Isometric Contraction; D007668:Kidney / Q000098:blood supply*; D007866:Leg; D008297:Male; D009470:Muscle Spindles / Q000502:physiology*; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism; D012018:Reflex; D012077:Renal Artery / Q000502:physiology*; D012079:Renal Circulation; D013929:Thromboxane B2 / Q000378:metabolism; D014655:Vascular Resistance; D014661:Vasoconstriction
chemical_list: D013929:Thromboxane B2
keywords: exercise; mechanoreflex; muscle; renal vasoconstriction; stretch