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Chloroform extract of hog barn dust modulates skeletal muscle ryanodine receptor calcium-release channel (RyR1).

Authors
Tian-C; Shao-CH; Fenster-DS; Mixan-M; Romberger-DJ; Toews-ML; Bidasee-KR
Source
J Appl Physiol 2010 Sep; 109(3):830-839
NIOSHTIC No.
20038185
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 Ca2+-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 HBDorg, were air-dried and studied further. In competition assays, HBDorg dose-dependently displaced [3H]ryanodine from binding sites on RyR1 with an IC50 of 1.5+/-0.1 microg/ml (Ki=0.4+/-0.0 microg/ml). In single-channel assays using RyR1 reconstituted into a lipid bilayer, HBDorg 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 C2C12 myotubes, addition of HBD triggered a rise in intracellular Ca2+ 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.
Keywords
Musculoskeletal-system-disorders; Animal-husbandry; Animal-husbandry-workers; Respirable-dust; Agricultural-industry; Agricultural-workers; Dusts; Cellular-function; Muscle-function; Solvents; Bioassays; Dose-response; Lipids; Cellular-reactions; Muscle-cells; Chemical-binding; Author Keywords: muscle weakness; single channel; binding; C2C12 cells
Contact
K. R. Bidasee, 985800 Nebraska Medical Center, Durham Research Center, DRC 3047, Omaha, NE 68198-5800
CODEN
JAPHEV
CAS No.
7440-70-2; 67-66-3
Publication Date
20100901
Document Type
Journal Article
Email Address
kbidasee@unmc.edu
Funding Type
Grant
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-008539
Issue of Publication
3
ISSN
8750-7587
Priority Area
Agriculture, Forestry and Fishing
Source Name
Journal of Applied Physiology
State
NE
Performing Organization
University of Nebraska
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