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Effects of silica exposure on substance p immunoreactivity and preprotachykinin mRNA expression in trigeminal sensory neurons in Fischer 344 rats.

Authors
Hunter-DD; Castranova-V; Stanley-C; Dey-RD
Source
J Toxicol Environ Health, A 1998 Apr; 53(8):593-605
NIOSHTIC No.
20024991
Abstract
Trigeminal sensory neurons innervate the nasal cavity and may release substance P (SP) upon exposure to inhaled irritants. The purpose of this study was to determine if silica dust, an occupational irritant causing inflammation, activates sensory neurons supplying the nasal cavity. Male Fischer 344 rats were placed in inhalation chambers and exposed daily to 2 mg/m3 of fresh silica (average diameter 1 mum) for 6 mo. Following exposure, the trigeminal ganglia (TG) were removed and prepared for SP immunocytochemistry and for preprotachykinin (PPT) autoradiographic in situ hybridization. The SP-like immunofluorescence in TG neurons was subjectively categorized as high, moderate, or low ( background) intensity. In situ hybridization autoradiographs were quantified on the basis of grain density using digital imaging analysis. The SP immunoreactivity and PPT mRNA expression in the TG neurons were significantly increased after silica inhalation. The proportion of highly positive SP-immunoreactive neurons shifted from 1.30 +/- 0.58% in controls to 11.30 +/- 1.15% after silica treatment. The neurons exhibiting high grain density for PPT mRNA increased from 1.50 +/- 0.87% in controls to 11.67 +/- 0.58% in the silica group. Thus, inhalation of silica causes upper airway irritation resulting in increased levels of immunoreactive neuronal SP and PPT mRNA. These findings suggest that silica activates sensory pathways that may be involved in nasal inflammation.
Keywords
Inhalation-studies; Inhalants; Nasal-cavity; Nasal-disorders; Silica-dusts; Silicates; Animals; Animal-studies
Contact
Dr. Richard D. Dey, P.O Box 9128, Morgantown, WV 26505-9128
CODEN
JTEHD6
Publication Date
19980415
Document Type
Journal Article
Email Address
rdey@wvu.edu
Fiscal Year
1998
NTIS Accession No.
NTIS Price
Issue of Publication
8
ISSN
0098-4108
NIOSH Division
HELD
Source Name
Journal of Toxicology and Environmental Health, Part A: Current Issues
State
WV
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