Abstract Skeletal muscle weakness is a reported ailment in individuals working in commercial hog confinement facilities. To date, specific mechanisms responsible for this symptom remain undefined. The purpose of this study was to assess whether hog barn dust (HBD) contains components that are capable of binding to and modulating the activity of type 1 ryanodine receptor Ca 2+ -release channel (RyR1), a key regulator of skeletal muscle function. HBD collected from confinement facilities in Nebraska were extracted with chloroform, filtered, and rotary evaporated to dryness. Residues were resuspended in hexane-chloroform (20:1) and precipitates, referred to as HBD org , were air-dried and studied further. In competition assays, HBD org dose-dependently displaced 3 Hryanodine from binding sites on RyR1 with an IC 50 of 1.5 ± 0.1 μg/ml ( K i = 0.4 ± 0.0 μg/ml). In single-channel assays using RyR1 reconstituted into a lipid bilayer, HBD org exhibited three distinct dose-dependent effects: first it increased the open probability of RyR1 by increasing its gating frequency and dwell time in the open state, then it induced a state of reduced conductance (55% of maximum) that was more likely to occur and persist at positive holding potentials, and finally it irreversibly closed RyR1. In differentiated C 2 C 12 myotubes, addition of HBD triggered a rise in intracellular Ca 2+ that was blocked by pretreatment with ryanodine. Since persistent activation and/or closure of RyR1 results in skeletal muscle weakness, these new data suggest that HBD is responsible, at least in part, for the muscle ailment reported by hog confinement workers. muscle weakness single channel binding C 2 C 12 cells Copyright © 2010 the American Physiological Society
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Chloroform extract of hog barn dust modulates skeletal muscle ryanodine receptor calcium-release channel (RyR1)
Tian, Chengju; Shao, Chun Hong; Fenster, Danielle S.; Mixan, Mark; Romberger, Debra J.; Toews, Myron L.; Bidasee, Keshore R.
Follow Journal of Applied Physiology
, Volume 109 (3): 830
The American Physiological Society – Sep 1, 2010
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