Vibration Causes Acute Vascular Injury in a Two‐Step Process: Vasoconstriction and Vacuole Disruption

Abstract

Hand-arm vibration syndrome is a vasospastic and neurodegenerative occupational disease. In the current study, the mechanism of vibration-induced vascular smooth muscle cell (SMC) injury was examined in a rat-tail vibration model. Tails of male Sprague Dawley rats were vibrated continuously for 4 hr at 60 Hz, 49 m/s 2 with or without general anesthesia. Ventral tail arteries were aldehyde fixed and embedded in epoxy resin to enable morphological analysis. Vibration without anesthesia caused vasoconstriction and vacuoles in the SMC. Anesthetizing rats during vibration prevented vasoconstriction and vacuole formation. Exposing tail arteries in situ to 1 mM norepinephrine (NE) for 15 min induced the greatest vasoconstriction and vacuolation. NE induced vacuoles were twice as large as those formed during vibration. When vibrated 4 hr under anesthesia after pretreatment with NE for 15 min, the SMC lacked vacuoles and exhibited a longitudinal banding pattern of dark and light staining. The extracellular matrix was filled with particulates, which were confirmed by electron microscopy to be cellular debris. The present findings demonstrate that vibration-induced vasoconstriction (SMC contraction) requires functioning central nervous system reflexes, and the physical stress of vibration damages the contracted SMC by dislodging and fragmenting SMC vacuoles. Anat Rec, 291:999

Vibration Disrupts Vascular Function in a Model of Metabolic Syndrome

“…Acute exposure to vibration also results in a transient vasoconstriction and reductions in finger blood flow in humans 21) . Bouts of vasoconstriction induced by single exposures to vibration have been associated with vacuole formation and disruption of the endothelial cell layer in animals 22) . However, it is unclear if these acute bouts of vasoconstriction and morphological changes in peripheral arteries contribute to the vascular dysfunction associated with VWF.…”

Dependence of Vascular Damage on Higher Frequency Components in the Rat-tail Model

“…Vacuole Count. Plastic-embedded semi-thin artery sections (1 μm) were used for toluidine blue staining and further for counting vacuoles (2-12 μm in size) 11,13) under a light microscope. The artery sections were stained with 1% toluidine blue for two minutes, rinsed with deionized water and cover-slipped.…”

“…Several earlier reports investigating vascular damage centered on the frequency of 60 Hz 8,[10][11][12][13][14] , whereas higher frequency components in the range between 125 Hz and 250 Hz have gained increasing attention only recently 9,15,16) . The cellular events responsible for early pathological damage in vasculature are still unclear for the frequencies near resonance range (125-250 Hz), which seem to play a key role in eliciting degenerative changes in the vascular tissue.…”

Evaluation of anti-vibration interventions for the hand during sheet metal assembly work

“…Occupational hand-transmitted vibration exposure has been linked to serious neurologic and vascular symptoms including hand-arm vibration syndrome and carpal tunnel syndrome [1][2][3][4][5][6][7][8]. Recent studies suggest that higher frequencies of vibration may result in damage to the smaller blood vessels of the hand [9][10][11]. Prevention of vibration exposures is most effectively managed through engineering controls [12], though tool modifications and development of hands-free work methods are costly and may not be feasible.…”